System and method for purging a fuel manifold of a gas turbine engine using a pump

ABSTRACT

Methods and systems of operating a gas turbine engine in a low-power condition are provided. In one embodiment, the method includes supplying fuel to a combustor by supplying fuel to a first fuel manifolds and a second fuel manifold of the gas turbine engine. The method also includes, while supplying fuel to the combustor by supplying fuel to the first fuel manifold: stopping supplying fuel to the second fuel manifold; and using a pump to drive gas into the second fuel manifold to flush fuel in the second fuel manifold into the combustor and hinder coking in the second fuel manifold and associated fuel nozzles.

CROSS REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

The present application claims priority to: U.S. provisional patentapplication No. 62/848,187 filed on May 15, 2019 and incorporated hereinby reference; U.S. provisional patent application No. 62/848,196 filedon May 15, 2019 and incorporated herein by reference; U.S. provisionalpatent application No. 62/848,223 filed on May 15, 2019 and incorporatedherein by reference; U.S. provisional patent application No. 62/850,809filed on May 21, 2019 and incorporated herein by reference; U.S.provisional patent application No. 62/848,231 filed on May 15, 2019 andincorporated herein by reference; and to U.S. provisional patentapplication No. 62/849,428 filed on May 17, 2019 and incorporated hereinby reference.

TECHNICAL FIELD

The disclosure relates generally to gas turbine engines, and moreparticularly to the operation of gas turbine engines at low powerconditions.

BACKGROUND OF THE ART

Twin-engine helicopters are provided with two turboshaft gas turbineengines. The outputs of both engines are connected to drive a main rotorof the helicopter via a reduction gearbox. Each of the engines is sizedto account for a worst-case scenario of the other engine failing duringtakeoff. Accordingly, the power rating of each engine is significantlygreater than what is required for cruising.

During a cruise operating regime (phase of flight), operating only oneof the two engines at a relatively high power regime instead of bothengines at a lower power regime can provide better fuel efficiency.However, once a turboshaft engine is stopped, there is an amount of timerequired to restart the engine and have the engine running at asufficient output power level to make up for a possible power drop ofthe other engine. Even though only one of the two engines may berequired during the cruise operating regime, it is typically requiredfor safety reasons that both engines remain operating at all timesduring flight. Accordingly, in an emergency condition such as a powerdrop in one of the two engines, this allows the other engine to rapidlyincrease its power output to provide power to make up for the powerloss. However, having both engines operating at all times during flightcan limit the gains in fuel efficiency. Also, further improvements inreliability and maintenance requirements are desirable.

SUMMARY

In one aspect, there is provided a method of operating a gas turbineengine, the gas turbine engine having a first fuel manifold and a secondfuel manifold configured to supply fuel to a combustor of the gasturbine engine. The method comprises:

supplying fuel to the combustor by supplying fuel to the first andsecond fuel manifolds;

while supplying fuel to the combustor by supplying fuel to the firstfuel manifold: stopping supplying fuel to the second fuel manifold; and

using a pump to drive gas into the second fuel manifold to flush fuel inthe second fuel manifold into the combustor.

In another aspect, there is provided a method of operating amulti-engine system of an aircraft, the multi-engine system including afirst gas turbine engine (FGTE) and a second gas turbine engine (SGTE)drivingly connected to a common load. The method comprises:

operating the FGTE and the SGTE to drive the common load, operating theSGTE including supplying fuel to a combustor of the SGTE by supplyingfuel to a first fuel manifold and a second fuel manifold of the SGTE;

while operating the FGTE and supplying fuel to the combustor of the SGTEby supplying fuel to the first fuel manifold of the SGTE:

stopping supplying fuel to the second fuel manifold of the SGTE; and

using a pump to drive gas into the second fuel manifold of the SGTE toflush fuel in the second fuel manifold into the combustor of the SGTE.

In a further aspect, there is provided a fuel system of a gas turbineengine. The fuel system comprises:

a first fuel manifold configured to supply fuel to a combustor of thegas turbine engine;

a second fuel manifold configured to supply fuel to the combustor;

one or more valves actuatable between a first configuration and a secondconfiguration, the one or more valves configured to supply fuel to thefirst and second fuel manifolds in the first configuration, the one ormore valves configured to supply fuel to the first fuel manifold andstop supplying fuel to the second fuel manifold in the secondconfiguration; and

a pump configured to, in the second configuration of the one or morevalves, drive gas into the second fuel manifold to flush fuel in thesecond fuel manifold into the combustor.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIG. 1 is a schematic cross-sectional view of a multi-engine power plantincluding a fuel system as described herein;

FIG. 2 is a schematic illustration of an exemplary fuel system of a gasturbine engine;

FIG. 3 is a schematic illustration showing another exemplary fuel systemof a gas turbine engine;

FIG. 4 is a flowchart of an exemplary method of operating a gas turbineengine;

FIG. 5 is a flowchart of an exemplary method of operating a multi-enginepower plant of an aircraft;

FIG. 6 is a schematic illustration of another exemplary fuel system of agas turbine engine;

FIG. 7 is a flowchart of another exemplary method of operating a gasturbine engine;

FIG. 8 is a flowchart of another exemplary method of operating amulti-engine power plant;

FIG. 9 is a schematic illustration of another exemplary fuel system of agas turbine engine;

FIG. 10 is a flowchart of another exemplary method of operating a gasturbine engine;

FIG. 11 is a flowchart of another exemplary method of operating a gasturbine engine;

FIG. 12 is a flowchart of another exemplary method of operating amulti-engine power plant;

FIG. 13 is a schematic illustration of another exemplary fuel system ofa gas turbine engine;

FIG. 14 is a flowchart of another exemplary method of operating a gasturbine engine;

FIG. 15 is a flowchart of another exemplary method of operating amulti-engine power plant;

FIG. 16 is a schematic cross-sectional view of another fuel system of agas turbine engine;

FIGS. 17A-17C are schematic cross-sectional views of an exemplary flowdivider valve in first, second and third configurations respectively;

FIGS. 18A-18C are schematic cross-sectional views of another exemplaryflow divider valve in first, second and third configurationsrespectively;

FIGS. 19A-19D are schematic cross-sectional views of another exemplaryflow divider valve in first, second, third and fourth configurationsrespectively;

FIGS. 20A-20C are schematic cross-sectional views of another exemplaryflow divider valve in first, second and third configurationsrespectively;

FIGS. 21A-21C are schematic cross-sectional views of another exemplaryflow divider valve in first, second and third configurationsrespectively;

FIGS. 22A-22C are schematic cross-sectional views of another exemplaryflow divider valve in first, second and third configurationsrespectively;

FIGS. 23A-23C are schematic cross-sectional views of another exemplaryflow divider valve in first, second and third configurationsrespectively;

FIGS. 24A-24C are schematic cross-sectional views of another exemplaryflow divider valve in first, second and third configurationsrespectively; and

FIGS. 25A-25C are schematic cross-sectional views of another exemplaryflow divider valve in first, second and third configurationsrespectively.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates an exemplary multi-engine (e.g.,twin-pack) power plant 42 that may be used for an aircraft 22, which maybe a rotorcraft such as a helicopter. The multi-engine power plant 42may include two or more GTEs 10A, 10B. The first gas turbine engine 10Ais referred hereinafter as “FGTE 10A” and the second gas turbine engine10B is referred hereinafter as “SGTE 10B”. In some instances FTGE 10Aand/or SGTE 10B may be referred to generically as GTE 10 or GTEs 10A,10B. In the case of a helicopter application, these GTEs 10A, 10B may beturboshaft engines. However, it is understood that methods, systems andcomponents disclosed herein are applicable to other types of aircraftengines such as turbofans and turboprops for example.

FIG. 1 shows axial cross-section views of two exemplary GTEs 10A, 10B ofthe turboshaft type. Each of the GTEs 10A, 10B may comprise, in serialflow communication, respectively, air intake 12A, 12B through whichambient air is received, multistage compressor section 14A, 14B(referred generically as “compressor section 14”) for pressurizing theair, combustor 16A, 16B (referred generically as “combustor 16”) inwhich the pressurized air is mixed with fuel and ignited for generatingan annular stream of hot combustion gases, and one or more turbines 18A,18B for extracting energy from the combustion gases. In someembodiments, GTEs 10A, 10B may be of the same type and power outputrating.

Control of the multi-engine power plant 42 is effected by one or morecontroller(s) 29, which may be full authority digital enginecontroller(s) (FADEC(s)), electronic engine controller(s) (EEC(s)), orthe like, that is/are programmed to manage, as described herein below,the operation of the GTEs 10A, 10B to reduce an overall fuel burn,particularly during sustained cruise operating regimes, wherein theaircraft 22 is operated at a sustained (steady-state) cruising speed andaltitude. The cruise operating regime is typically associated with theoperation of prior art engines at equivalent part-power, such that eachengine contributes approximately equally to the output power of thepower plant 42. Other phases of a typical helicopter mission includetransient phases like take-off, climb, stationary flight (hovering),approach and landing. Cruise may occur at higher altitudes and higherspeeds, or at lower altitudes and speeds, such as during a search phaseof a search-and-rescue mission.

In the present description, while the aircraft conditions (cruise speedand altitude) are substantially stable, the GTEs 10A, 10B of the powerplant 42 may be operated asymmetrically, with one engine operated in ahigh-power “active” mode and the other engine operated in a low power(which could be no power, in some cases) “standby” mode. Doing so mayprovide fuel saving opportunities to the aircraft 22, however there maybe other suitable reasons why the GTEs 10A, 10B are desired to beoperated asymmetrically. This operation management may therefore bereferred to as an “asymmetric mode” or an “asymmetric operating regime”,wherein one of the two GTEs 10A, 10B is operated in a low power (whichcould be no power, in some cases) “standby mode” while the other FGTE10A or SGTE 10B is operated in a high-power “active” mode. In such anasymmetric operation, which is engaged for a cruise operating regime(continuous, steady-state flight which is typically at a given commandedconstant aircraft cruising speed and altitude). The multi-engine powerplant 42 may be used in an aircraft, such as a helicopter, but also hasapplications in suitable marine and/or industrial applications or otherground operations.

Referring still to FIG. 1, according to the present description, themulti-engine power plant 42 is driving, in this example, a helicopterand may be operated in this asymmetric manner, in which a first of theGTEs 10 (say, 10A) may be operated at high power in an active mode andthe second of the GTEs 10 (10B in this example) may be operated in a lowpower (which could be no power, in some cases) standby mode. In oneexample, the FGTE 10A may be controlled by the controller(s) 29 to runat full (or near-full) power conditions in the active mode, to supplysubstantially all or all of a required power and/or speed demand of thecommon load 44. The SGTE 10B may be controlled by the controller(s) 29to operate at low power or no-output-power conditions to supplysubstantially none or none of a required power and/or speed demand ofthe common load 44. Optionally, a clutch may be provided to declutch thelow-power standby SGTE 10B. Controller(s) 29 may control the engine'sgoverning on power according to an appropriate schedule or controlregime. The controller(s) 29 may comprise a first controller forcontrolling the FGTE 10A and a second controller for controlling theSGTE 10B. The first controller and the second controller may be incommunication with each other in order to implement the operationsdescribed herein. In some embodiments, a single controller 29 may beused for controlling the first FGTE 10A and the SGTE 10B.

In another example, an asymmetric operating regime of the GTEs 10A, 10Bmay be achieved through the one or more controller's 29 differentialcontrol of fuel flow to the GTEs 10A, 10B, as described in U.S. PatentPublication no. US 2020/0049025 A1 titled “MULTI-ENGINE SYSTEM ANDMETHOD”, the entire contents of which are incorporated herein byreference. Low fuel flow may also include zero fuel flow in someexamples.

Although various differential control between the GTEs 10A, 10B of theengine power plant 42 are possible, in one particular embodiment thecontroller(s) 29 may correspondingly control fuel flow rate to each GTE10A, 10B accordingly. In the case of the standby SGTE 10B, a fuel flow(and/or a fuel flow rate) provided to the standby SGTE 10B may becontrolled to be between 70% and 99.5% less than the fuel flow (and/orthe fuel flow rate) provided to the active FGTE 10A. In the asymmetricmode, the standby SGTE 10B may be maintained between 70% and 99.5% lessthan the fuel flow to the active FGTE 10A. In some embodiments of thesystems and methods disclosed herein, the fuel flow rate differencebetween the active and standby GTEs 10A, 10B may be controlled to be ina range of 70% and 90% of each other, with fuel flow to the standby SGTE10B being 70% to 90% less than the active FGTE 10A. In some embodiments,the fuel flow rate difference may be controlled to be in a range of 80%and 90%, with fuel flow to the standby SGTE 10B being 80% to 90% lessthan the active FGTE 10A.

In another embodiment, the controller 29 may operate one engine (saySGTE 10B) of the multi-engine power plant 42 in a standby mode at apower substantially lower than a rated cruise power level of the SGTE10B, and in some embodiments at substantially zero output power and inother embodiments less than 10% output power relative to a referencepower (provided at a reference fuel flow). Alternately still, in someembodiments, the controller(s) 29 may control the standby SGTE 10B tooperate at a power in a range of 0% to 1% of a rated full-power of thestandby SGTE 10B (i.e. the power output of the standby SGTE 10B to thecommon gearbox 52 remains between 0% to 1% of a rated full-power of thestandby SGTE 10B when the standby SGTE 10B is operating in the standbymode).

In another example, the multi-engine power plant 42 of FIG. 1 may beoperated in an asymmetric operating regime by control of the relativespeed of the GTEs 10A, 10B using controller(s) 29, that is, the standbySGTE 10B is controlled to a target low speed and the active FGTE 10A iscontrolled to a target high speed. Such a low speed operation of thestandby SGTE 10B may include, for example, a rotational speed that isless than a typical ground idle speed of the engine (i.e. a “sub-idle”engine speed). Still other control regimes may be available foroperating the GTEs 10A, 10B in the asymmetric operating regime, such ascontrol based on a target pressure ratio, or other suitable controlparameters.

Although the examples described herein illustrate two GTEs 10A, 10B,asymmetric mode is applicable to more than two engines, whereby at leastone of the multiple engines is operated in a low-power standby modewhile the remaining engines are operated in the active mode to supplyall or substantially all of a required power and/or speed demand of acommon load.

In use, the first turboshaft engine (say FTGE 10A) may operate in theactive mode while the other turboshaft engine (say SGTE 10B) may operatein the standby mode, as described above. During this asymmetricoperation, if the helicopter needs a power increase (expected orotherwise), the SGTE 10B may be required to provide more power relativeto the low power conditions of the standby mode, and possibly returnimmediately to a high- or full-power condition. This may occur, forexample, in an emergency condition of the multi-engine power plant 42powering the helicopter, wherein the active engine loses power andtransitioning the standby engine from the low power condition to thehigh power condition may occur rapidly. Even absent an emergency, itwill be desirable to repower the standby engine to exit the asymmetricmode.

During the low power (standby) operation or shutdown of a GTE 10, fuelflow rates through one or more fuel manifolds feeding fuel to fuelnozzles of the GTE 10 may need to be lowered significantly or stopped.If sufficiently low or stopped, residual or slow flowing fuel in therespective fuel manifolds and nozzles may form soot due to exposure tohigh combustor temperatures or direct combustion. Such type of sootformation is called coking and can degrade performance of the nozzlesand fuel manifolds by clogging fuel flow pathways with carbon depositsover time. One or both of the GTEs 10A, 10B may include a fuel system50A, 50B that is configured to mitigate and/or hinder such coking.Various embodiments of such fuel system, associated methods andcomponents are described herein. The low-power (standby) operation mayinclude non-shutting down, continued operation, and/or sustainedoperation of a GTE 10.

FIG. 2 is a schematic illustration of an exemplary fuel system 50 (e.g.,fuel system 50A and/or fuel system 50B) of a GTE 10 (e.g., FGTE 10Aand/or SGTE 10B) mounted to the aircraft 22. The fuel system 50 mayinclude a first fuel manifold 62A fluidly connected to and configured tosupply fuel to a combustor 16 of the GTE 10, and also a second fuelmanifold 62B fluidly connected to and configured to supply fuel to thesame combustor 16. In some embodiments, the fuel manifolds 62A, 62B maysupply fuel to the combustor 16 via respective one or more sets of fuelnozzles 61A, 61B opening into the combustor 16. In some embodiments,first and second sets of fuel nozzles 61A, 61B may be substantially thesame or different. In some operating situations, different amounts offuel may be supplied to the first and second fuel manifolds 62A, 62B.

The fuel system 50 may include an arrangement 73 of valves including oneor more flow divider valves 66 that may or may not be part of a valveassembly. The flow divider valve 66 may be a hydraulic device, anelectronic device or an electronically-controlled hydraulic device thatcan separate a flow into two or more parts, e.g., according to apredetermined schedule. The arrangement 73 and/or flow divider valve 66may comprise one or more embodiments of (flow divider) valves, orassemblies, described herein, such as embodiments described in FIGS.16-25C.

The arrangement 73 of valves may include one or more valves and beconfigurable (e.g., actuatable) between a first configuration and asecond configuration. The arrangement 73 of valves may include one ormore purge valves 70, which may include a solenoid-operated valve, oneor more (e.g., a plurality) of one-way valves 72A, 72B, an optional(pressure or flow) regulator 68, a flow divider valve 66, flow divertervalve(s), and/or any other flow control device(s) configured topermit/stop/regulate fluid flow or pressure across the arrangement 73 ofvalves. The arrangement 73 of valves may be configured to supply fuel tothe first and second fuel manifolds 62A, 62B in the first configurationof the arrangement 73 of valves. The arrangement 73 of valves may beconfigured to supply fuel to the first fuel manifold 62A and stopsupplying fuel to the second fuel manifold 62B in the secondconfiguration.

The first configuration of the arrangement 73 of valves may be adoptedduring a high-power “active” mode of the GTE 10. The first configurationmay facilitate operating the multi-engine power plant 42 at high orintermediate power levels during flight, i.e. wherein all or most of theengines of the multi-engine power plant 42 receive fuel and producesignificant and useful work to drive the common load 44 (shown in FIG.1).

The second configuration of the arrangement 73 of valves may be adoptedduring the low power “standby” mode of the GTE 10. The secondconfiguration may facilitate operating the multi-engine power plant 42in the asymmetric operating regime described above. The secondconfiguration of the arrangement 73 of valves may be used to bring theGTE 10 to the standby mode of operation by supplying fuel to thecombustor 16 via only the first fuel manifold 62A and not via the secondfuel manifold 62B. In some situations, the use of only one (or some) ofthe fuel manifolds 62A, 62B may require less fuel to keep the standbyGTE 10 running in the standby mode as opposed to having to keep fuelflowing to all of the fuel manifolds 62A, 62B of the standby GTE 10.

The fuel system 50 may include an accumulator 64 (e.g., reservoir,pressure vessel) configured to store pressurized air (or other suitablepressurized gas). In the second configuration of the arrangement 73 ofvalves, the accumulator 64 may fluidly connect to the second fuelmanifold 62B to discharge pressurized air (e.g., allow flow ofpressurized air) into the combustor 16 via the second fuel manifold 62Bto flush (push) residual fuel in the second fuel manifold 62B (and/orfuel nozzles 61B) into the combustor 16 after fuel supply to the secondfuel manifold 62B has been stopped.

The fuel system 50 may comprise a fuel line 76B establishing fluidcommunication between a first of the one or more valves (e.g., one-wayvalve 72B or flow divider valve 66 in the arrangement 73 of valves) andthe second fuel manifold 62B. The fuel source may be configured toprovide fuel flow to the first and second fuel manifolds 62A, 62B viathe upstream fuel line 76A and the flow divider valve 66. The flowdivider valve 66 may supply fuel to the first fuel manifold 62A via thedownstream fuel line 76C, and to the second fuel manifold 62B via thedownstream fuel line 76B. A fuel pump (not shown) may be operativelydisposed between the fuel source and the flow divider valve 66.

The accumulator 64 may be configured to discharge pressurized air intothe downstream fuel line 76B at a location 75 downstream of the flowdivider valve 66 in the second configuration of the arrangement 73 ofvalves.

The accumulator 64 may be configured to receive and be charged withpressurized gas from a pressurized gas source 58 prior to thearrangement 73 of valves entering the second (purge) configuration. Thepressurized gas source 58 may be a compressor section 14A or 14B of theGTE 10A or 10B and the pressurized gas may be pressurized air. Theaccumulator 64 may fluidly connect to the compressor section 14 toreceive pressurized air from the compressor section 14. In someembodiments, pressurized air may be bleed air drawn from a gas path ofGTE 10 at a location upstream of combustor 16. In some embodiments,pressurized gas source 58 may be another pressurized gas generator suchas another compressor (e.g., pump) for example. For example, theaccumulator 64 may be configured to receive relatively high-pressure airfrom a later or last stage of compression of the compressor section 14of the same or another GTE 10. The charging of the accumulator 64 withpressurized air may be conducted while the soon-to-be standby GTE 10 isoperating at a higher power output level so that the pressure inside theaccumulator 64 may be higher than in the combustor 16 while purging thefuel at the lower power output level in order to enable purging of thefuel from the fuel manifold 62B (and/or fuel nozzles 61B) into thecombustor 16 using the pressurized air inside the accumulator 64.Additionally, fuel system 50 may include one or more one-way valves 72Band/or one or more regulators 68 which may be configured to preventbackflows such as backflow of fuel and/or combustion gas from the fuelmanifold 62B (and/or fuel nozzles 61B) toward the accumulator 64.

Flushing fuel from the fuel manifold 62B may include substantiallyemptying the fuel manifold 62B (and/or fuel nozzles 61B) of fuel. Insome embodiments, flushing fuel from the fuel manifold 62B may includedrying the fuel manifold 62B and fuel nozzles 61B. While the fuelmanifold 62B is flushed of fuel and fuel supply thereto is stopped,continuing combustion in the combustor 16, e.g., fed by fuel flowing tothe combustor 16 via the first fuel manifold 62A, may reduce the amountof coking in the second fuel manifold 62B and fuel nozzles 61B due tothe lack of fuel inside the second fuel manifold 62B and fuel nozzles61B. Thus, the second fuel manifold 62B may be kept empty of fuel duringoperation of the GTE 10 (e.g., during flight or a cruise regime duringflight) in the standby mode without causing significant coking insidethe second fuel manifold 62B and/or fuel nozzles 61B. Accordingly, incertain instances, when a minimal amount of fuel needed for sustainingcombustion is supplied to the combustor 16 via the first fuel manifold62A only, an energy efficient low power standby mode of the GTE 10 maybe achieved without significant coking of the purged second fuelmanifold 62B.

Since combustion is sustained in the combustor 16 via the first fuelmanifold 62A, the standby GTE 10 may in some instances retain theability to more quickly provide a demanded power increase via a rapid“spool-up”, while minimizing or significantly reducing fuel consumptionin intervening periods when such power is not required. Spooling-up ofthe GTE 10, or otherwise changing the operation of the GTE 10 away fromthe standby mode, may include changing a configuration of thearrangement 73 of valves to the first configuration described above.

In some embodiments, the fuel system 50 includes a controller 29. Thecontroller 29 may be operatively coupled to the arrangement 73 of valvesor to one or more of the components of the arrangement 73 of valves. Insome embodiments, the controller 29 may trigger the purge valve 70 toopen a gas pathway 77 between the accumulator 64 to the fuel manifold62B to enable fuel purging therein by pressurized gas flowing theretofrom the accumulator 64.

In some embodiments, the one-way valve 72A may be positioned between thepressurized gas source 58 (e.g., compressor section 14) and theaccumulator 64. The one-way valve 72A may prevent backflow from theaccumulator 64 to the pressurized gas source 58 in the event of areduction in supply pressure of the pressurized gas source 58. In someembodiments, the one-way valve 72B may be positioned between theaccumulator 64 and the fuel manifold 62B (e.g., upstream of downstreamfuel line 76B in the gas pathway 77) to prevent fuel from flowing to theaccumulator 64 and/or the pressurized gas source 58.

In some embodiments, the regulator 68 may be operatively disposedbetween the accumulator 64 and the fuel manifold 62B, downstream of theaccumulator 64 and upstream of the fuel manifold 62B. In someembodiments, the regulator 68 may be a flow regulator configured tocontrol flow/volume rate, or a pressure regulator configured to controla downstream (flow/fluid) pressure. The regulator 68 may allow controlof the flow, e.g., it may prevent flow pressure from exceeding orfalling below a certain pressure. In some embodiments, the regulator 68may be a single stage pressure regulator. In some embodiments, theregulator 68 may be an electrically-controlled valve such as a solenoidvalve. In various embodiments, regulator 68 may include any suitablemeans of flow regulation. In some embodiments, regulator 68 may be of atype suitable for maintaining or controlling a downstream pressure ofgas delivered to the fuel manifold 62B.

In some embodiments, the fuel system 50 may be configured to controlpressurized gas/air flow to the fuel manifold 62B (for flushing fuelinto the combustor 16) in a manner that avoids engine surge caused by afuel spike in the combustor 16. An engine surge may be a momentary (orlonger lasting) increase in power output of the GTE 10. The fuel spikein the combustor 16 may be a relatively sudden (e.g., rapid, abrupt,sharp) increase of fuel flow to the combustor 16. The use of theregulator 68 may prevent or reduce the likelihood of the occurrence ofsuch fuel spike. For example, the regulator 68 may prevent a suddenburst of pressurized air from being discharged into the fuel manifold62B which could cause such fuel spike. For example, the regulator 68 mayhelp maintain a fuel flow rate (flow rate of fuel) to the combustor viathe fuel manifold 62B below a threshold during purging. In other words,the fuel flow rate may be prevented from exceeding the threshold duringpurging. The threshold may be predetermined or not and may depend onoperating and atmospheric conditions (e.g., altitude or ambientpressure, flow rate of fuel to the combustor prior to flushing, gasturbine engine power level, etc.). The threshold may be determined toprevent an undesirable engine surge condition. In some embodiments, theregulator 68 may be configured to deliver pressurized gas according to adesired (e.g., constant and/or variable) purging pressure and/or flowdelivery schedule as a function of time.

FIG. 3 is a schematic illustration showing another exemplary fuel system150 of a GTE 10. Elements of the fuel system 150 that are similar toelements of the fuel system 50 described above are identified using likereference numerals. The GTE 10 may be the SGTE 10B. It is understoodthat a fuel system of the FGTE 10A may be different or substantiallyidentical to that of the SGTE 10B. The FGTE 10A and the SGTE 10B may bepart of the multi-engine power plant 42 configured to drive a commonload 44 of the aircraft 22. The fuel nozzles are not shown in FIG. 3.

The fuel system 150 may include an arrangement 173 of valves that may ormay not be part of a valve assembly. The arrangement 173 of valves maycomprise flow divider valve 166, and a purge (e.g., solenoid, hydraulic,or hydro-mechanical) valve 70 in a flow path between the flow dividervalve 166 and the pressurized gas source 58 via the optional accumulator64. The flow divider valve 166 may be controllable, directly orindirectly, by the controller 29. In a first configuration of thearrangement 173 of valves, the flow divider valve 66 may receive asupply of fuel from a fuel source and may supply fuel to the first andsecond fuel manifolds 62A, 62B. The first and second fuel manifolds 62A,62B may be fluidly connected to and configured to supply fuel to acombustor 16B of the SGTE 10B. The purge valve 70 may be closed in thefirst configuration of the arrangement 173 of valves. The arrangement173, flow divider valve(s) 166, and/or purge valve 70 may comprise oneor more embodiments of (flow divider) valves, or assemblies, describedherein, such as embodiments described in FIGS. 16-25C.

In a second configuration of the arrangement 173 of valves, the flowdivider valve 166 may continue receiving fuel from the fuel source(possibly at a lower fuel flow rate) but may also additionally receivepressurized gas from the accumulator 64 via the purge valve 70. In someembodiments, receiving pressurized gas from the accumulator 64 via thepurge valve 70 may be in addition to, or instead of, receivingpressurized gas from the pressurized gas source 58 via the purge valve70. The purge valve 70 may be open in the second configurationarrangement 173 of valves. In the second configuration, the flow dividervalve 166 may stop supplying fuel to the second fuel manifold 62B whilecontinuing to supply fuel to the first fuel manifold 62A (e.g., at a lowfuel flow rate to enable a standby condition of the SGTE 10B), and thenmay purge (flush) the second fuel manifold 62B of residual fuel bysupplying pressurized gas from the pressurized gas source 58 (e.g., viathe accumulator 64) to the second fuel manifold 62B to flush fueltherein into the combustor 16B of SGTE 10B.

The accumulator 64 may be charged with air/gas from a pressurized gassource 58 which may be part of or separate from SGTE 10B. Thepressurized gas source 58 may be a compressor section 14B or 14A of theSGTE 10B or of the FGTE 10A respectively. In some embodiments, theaccumulator 64 may be charged using pressurized air from the compressorsection 14A of FGTE 10A. In some embodiments, the accumulator 64 may becharged using pressurized air from the compressor section 14B of SGTE10B.

FIG. 4 is a flowchart of an exemplary method 2000 of operating a GTE 10.It is understood that aspects of method 2000 may be combined with othermethods, or aspects thereof, described herein. The GTE 10 may have afirst fuel manifold 62A and a second fuel manifold 62B configured tosupply fuel to the combustor 16 of the GTE 10.

The method 2000 includes supplying fuel to the combustor 16 by supplyingfuel to the first and second fuel manifolds 62A, 62B (at block 2100).The method 2000 includes stopping the supplying fuel to the second fuelmanifold 62B while supplying fuel to the combustor 16 by supplying fuelto the first fuel manifold 62A (at block 2200), and flushing fuel fromthe second fuel manifold 62B into the combustor 16 by dischargingpressurized air from an accumulator 64 into the second fuel manifold 62Bwhile supplying fuel to the combustor 16 by supplying fuel to the firstfuel manifold 62A (at block 2300).

In some embodiments of the method 2000, flushing residual fuel in thesecond fuel manifold 62B into the combustor 16 includes flushing orpurging fuel from fuel nozzles 61B in fluid communication with thesecond fuel manifold 62B, in order to prevent coking, soot formation, orany other (performance) degradation of fuel nozzles 61B arising due topresence of residual fuel therein when fuel supply to the second fuelmanifold 62B is stopped. Method 2000 may be used to transition the GTE10 from the high-power active mode of operation to the low power standbymode of operation.

Some embodiments of the method 2000 include using flow divider valve 66or 166 to stop supplying fuel to the second fuel manifold 62B and tosupply fuel to the first fuel manifold 62A.

In some embodiments of the method 2000, the GTE 10 is mounted to anaircraft 22 and the method 2000 is executed during flight of theaircraft 22. In an exemplary embodiment, the method 2000 is executedduring a sustained cruise operating regime of the aircraft 22, whereinthe aircraft 22 is operated at a sustained (steady-state) cruising speedand altitude. In some embodiments, the method 2000 may be executedduring other transient phases of flight, e.g., flight take-off, climb,stationary flight (hovering), approach and landing.

In some embodiments of the method 2000, the GTE 10 may be one (e.g.,SGTE 10B) of two GTEs 10A, 10B of a helicopter. The method 2000 mayinclude operating the SGTE 10B in a low power mode of operation whilefuel is supplied to the first fuel manifold 62A and fuel supply to thesecond fuel manifold 62B is stopped. The method 2000 may includeoperating the FGTE 10A in a high-power (e.g., active) mode of operationwhile the SGTE 10A is operated in the low power (e.g., standby) mode ofoperation.

Some embodiments of the method 2000 include, after fuel in the secondfuel manifold 62B is flushed into the combustor 16 and while continuingsupplying fuel to the combustor 16 by supplying fuel to the first fuelmanifold 62A, stopping discharging pressurized air from the accumulator64 into the second fuel manifold 62B. In some embodiments of the method2000, stopping discharging pressurized air may include letting theaccumulator 64 become empty. In some embodiments, stopping dischargingmay include shutting off the purge valve 70 to close a gas pathway 77.

Some embodiments of the method 2000 include, after stopping dischargingpressurized air from the accumulator 64 into the second fuel manifold62B and while continuing supplying fuel to the combustor 16 by supplyingfuel to the first fuel manifold 62B, initiating supplying fuel to thesecond fuel manifold 62B to resume supplying fuel to the combustor 16.In some of these embodiments of the method 2000, initiating supplyingfuel to the second fuel manifold 62B may be a part of a restart orspool-up of the GTE 10. In some of these embodiments of the method 2000,initiating supplying fuel to the second fuel manifold 62B may bechanging of the mode of operation of the GTE 10 from the low power(e.g., standby) mode to the high-power active mode.

Some embodiments of the method 2000 include discharging pressurized airfrom the accumulator 64 into a fuel line 76B (shown in FIG. 2)establishing fluid communication between the flow divider valve 66 andthe second fuel manifold 62B. In some of these embodiments of the method2000, discharging pressurized air may flush and dry the fuel line 76Band the second fuel manifold 62B of residual fuel, and may substantiallyprevent coking, during operation of the GTE 10, in components of thefuel system 50 exposed or open to the combustor 16.

Some embodiments of the method 2000 include, after fuel in the secondfuel manifold 62B is flushed into the combustor 16 and while supplyingfuel to the second fuel manifold 62B is stopped, continuing supplyingfuel to the combustor 16 by supplying fuel to the first fuel manifold62A. In some embodiments of the method 2000, the GTE 10 may continueoperating with only one fuel manifold 62A being supplied with fuelincluding during flight (when the GTE 10 is mounted to the aircraft 22),e.g., at a relatively low flow rate consistent with the low powerstandby mode of operation of the GTE 10.

Some embodiments of the method 2000 include, when fuel is being flushedinto the combustor 16, maintaining a fuel flow rate to the combustor 16via the second fuel manifold 62B below a threshold by controlling adischarge of pressurized air from the accumulator 64 and/or from apressurized gas source 58, e.g., to avoid a sudden burst of(pressurized) air into the fuel manifold 62B and maintain a fuel flowrate to the combustor 16 via the fuel manifold 62B being purged below athreshold as explained above. In some embodiments, controlling adischarge of pressurized air from the accumulator 64 may be based on afuel purging schedule including prescribed flow regulation ofpressurized gas flowing from the accumulator 64 as a function of time,such as time since stoppage of fuel supply to the second fuel manifold62B, or other event(s) such as engine power falling below or exceeding acertain level, or an operating condition of the GTE 10. In someembodiments of the method 2000, controlling a discharge of pressurizedair from the accumulator 64 and/or from the pressurized gas source 58may be achieved using the regulator 68.

Some embodiments of the method 2000 include charging the accumulator 64using pressurized air from a compressor section 14 of the same oranother GTE 10 prior to stopping supplying fuel to the second fuelmanifold 62B. In some embodiments of the method 2000, the accumulator 64may be charged using pressurized gas from the compressor section 14 ofthe same GTE 10 operating in a high-power active mode of operation.

FIG. 5 is a flowchart of an exemplary method 3000 of operating themulti-engine power plant 42 of an aircraft 22. It is understood thataspects of method 3000 may be combined with other methods, or aspectsthereof, described herein. The multi-engine power plant 42 includes theFGTE 10A and the SGTE 10B. The FGTE 10A and SGTE 10B are drivinglyconnected to a common load 44 (shown in FIG. 1). In some embodiments ofthe method 3000, the FGTE 10A and SGTE 10B are turboshaft engines. Insome embodiments of the method 3000, multi-engine power plant 42 may bemounted to aircraft 22 (e.g., helicopter).

The method 3000 includes operating the FGTE 10A and the SGTE 10B todrive the common load 44, operating the SGTE 10B including supplyingfuel to a combustor 16B of the SGTE 10B by supplying fuel to a firstfuel manifold 62A and a second fuel manifold 62B of the SGTE 10B (block3100). The method 3000 also includes stopping supplying fuel to thesecond fuel manifold 62B of the SGTE 10B during the operating the FGTE10A and the supplying fuel to the combustor 16B of the SGTE 10B bysupplying fuel to the first fuel manifold 62A of the SGTE 10B (block3200), and flushing fuel in the second fuel manifold 62B into thecombustor 16B of the SGTE 10B by discharging pressurized air from anaccumulator 64 into the second fuel manifold 62B of the SGTE 10B duringthe operating the FGTE 10A and the supplying fuel to the combustor 16Bof the SGTE 10B by the supplying fuel to the first fuel manifold 62A ofthe SGTE 10B (block 3300).

In some embodiments of the method 3000, operating the FGTE 10A mayinclude operating the FGTE 10A in the high-power active mode ofoperation.

Some embodiments of the method 3000 may include using a flow dividervalve 66 or 166 to stop supplying fuel to the second fuel manifold 62Band to supply fuel to the first fuel manifold 62A.

In some embodiments of the method 3000, the common load 44 may include arotary wing of the aircraft 22 and the method 3000 may be executedduring flight of the aircraft 22.

Some embodiments of the method 3000 may include, after fuel in thesecond fuel manifold 62B is flushed and while continuing supplying fuelto the combustor 16B of the SGTE 10B by supplying fuel to the first fuelmanifold 62A, stopping discharging pressurized air from the accumulator64 into the second fuel manifold 62B.

Some embodiments of the method 3000 may include, after stoppingdischarging pressurized air from the accumulator 64 into the second fuelmanifold 62B and while continuing supplying fuel to the combustor 16B ofthe SGTE 10B by supplying fuel to the first fuel manifold 62A,initiating supplying fuel to the second fuel manifold 62B to supply fuelto the combustor 16B of the SGTE 10B.

Some embodiments of the method 3000 may include discharging pressurizedair into a fuel line 76B establishing fluid communication between theflow divider valve 66 and the second fuel manifold 62B of the SGTE 10B.

Some embodiments of the method 3000 may include, when fuel is beingflushed into the combustor 16B of the SGTE 10B, maintaining a fuel flowrate to the combustor 16B via the second fuel manifold 62B below athreshold by controlling a discharge of pressurized air from theaccumulator 64 to prevent the delivery of a fuel spike to the combustor16B during purging.

In various embodiments described herein, the purging gas frompressurized gas source 58 may be pressurized air from a portion of oneor more of the gas turbine engines 10A, 10B or obtained from theatmosphere. However, it is understood that other types of purging gassessuch as CO₂ or N₂ may also be suitable.

FIG. 6 is a schematic illustration of another exemplary fuel system 250of a GTE 10 of a multi-engine power plant 42 (shown in FIG. 1) of anaircraft 22. Elements of the fuel system 250 that are similar toelements of the fuel system 50 described above are identified using likereference numerals. The GTE 10 may be the SGTE 10B. It is understoodthat a fuel system of the FGTE 10A may be different or substantiallyidentical to that of SGTE 10B. The FGTE 10A and the SGTE 10B may be partof the multi-engine power plant 42 configured to drive a common load 44of the aircraft 22.

The fuel system 250 includes one or more flow divider valves 66 disposedin a fuel line 76 (having a portion 76A upstream of the flow dividervalve 66 and a portion 76B downstream of the flow divider valve 66)connecting a fuel source to the second fuel manifold 62B. In someembodiments, the first fuel manifold 62A may be configured to receivefuel from the fuel source via the flow divider valve 66 or otherwise. Afuel pump (not shown) may be operatively disposed between the fuelsource and the flow divider valve 66.

The fuel system 250 may include a pressurized gas generator 78 disposedat one end of a gas pathway 77. The gas pathway 77 may be connected tothe fuel line 76B between the flow divider valve 66 and the second fuelmanifold 62B. Alternatively, the gas pathway 77 may be connected to thesecond fuel manifold 62B via the flow divider valve 66. The pressurizedgas generator 78 may be part of or separate from SGTE 10B. In variousembodiments, the pressurized gas generator 78 may be a pump including anaxial and/or centrifugal compressor, fan or blower for example. Thepressurized gas generator 78 may be driven (e.g., electrically,mechanically, pneumatically or hydraulically) by an electric, pneumaticor hydraulic motor. In some embodiments, the pressurized gas generator78 may be driven directly by an aircraft engine, e.g., the pressurizedgas generator 78 may be drivingly coupled to and mechanically driven bya shaft of the FGTE 10A or the SGTE 10B. The pressurized gas generator78 may be driven (e.g. actuated) or controlled electronically bycontroller(s) 29 for example.

The fuel system 250 may include one or more valves configurable (e.g.,actuatable) between a first configuration and a second configuration.The one or more valves may be configured to supply fuel to the first andsecond fuel manifolds 62A, 62B in the first configuration. The one ormore valves may be configured to supply fuel to the first fuel manifold62A and stop supplying fuel to the second fuel manifold 62B in thesecond configuration.

The fuel system 250 may include a one-way valve 72B disposed in the gaspathway 77 between the pressurized gas generator 78 and the fuel line76. The valve 72B may be configured to prevent fuel from flowing towardsthe pressurized gas generator 78. A portion 77A of the gas pathway 77may be connected to the pressurized gas generator 78 upstream of thevalve 72B and a portion 77B of the gas pathway 77 may be connected tothe fuel line 76B downstream of the flow divider valve 66) and/or viathe flow divider valve 66.

The multi-engine power plant 42 may be configured to operate in theasymmetric mode, during which the FGTE 10A is configured to operate in ahigh-power (active) mode and the SGTE 10B is configured to operate in alow power (standby) mode. During the asymmetric mode of operation, theflow divider valve 66 may be configured to stop supplying fuel to thesecond fuel manifold 62B while supplying fuel to the first fuel manifold62A. Furthermore, during the asymmetric mode, the pressurized gasgenerator 78 may be configured to supply pressurized gas to the secondfuel manifold 62B via the fuel line 76 (or 76B) to flush residual fuelin the second fuel manifold 62B into the combustor 16B.

The pressurized gas generator 78 may be driven continuously or may bepulsed until the fuel in a fuel line is purged, including when anaircraft engine is in operation. The fuel system 250 may be able toprovide an on-demand supply of air to dry and cool the fuel manifold(s)62A and/or 62B and associated nozzles feeding combustor 16B.

The flow divider valve(s) 66 and/or valve(s) 72B may comprise one ormore embodiments of (flow divider) valves, or assemblies, describedherein, such as embodiments described in FIGS. 16-25C.

FIG. 7 is a flowchart of a method 4000 of operating a GTE 10. It isunderstood that aspects of method 4000 may be combined with othermethods described herein. The GTE 10 has a first fuel manifold 62A and asecond fuel manifold 62B fluidly connected to and configured to supplyfuel to a combustor 16 of the GTE 10. The method 4000 includes supplyingfuel to the combustor 16 by supplying fuel to the first and second fuelmanifolds 62A, 62B (see block 4100). The method 4000 also includesstopping supplying fuel to the second fuel manifold 62B while (e.g.,continually) supplying fuel to the combustor 16 by supplying fuel to thefirst fuel manifold 62A (see block 4200). The method 4000 also includesusing a pressurized gas generator 78 (e.g., pump) to pressurize gaswhile (e.g., continually) supplying fuel to the combustor 16 bysupplying fuel to the first fuel manifold 62A (see block 4300). Themethod 4000 also includes supplying pressurized gas from the pressurizedgas generator 78 (e.g., a pump) to the second fuel manifold 62B to flushfuel in the second fuel manifold 62B into the combustor 16 while (e.g.,continually) supplying fuel to the combustor 16 by supplying fuel to thefirst fuel manifold 62A (see block 4400).

Some embodiments of the method 4000 include using a flow divider valve66 or 166 to stop supplying fuel to the second fuel manifold 62B and tosupply fuel to the first fuel manifold 62B.

Some embodiments of the method 4000 include increasing the supply offuel to the first fuel manifold 62A when stopping supplying fuel to thesecond fuel manifold 62B.

In some embodiments of the method 4000, the GTE 10 is mounted to anaircraft 22 (e.g., helicopter) and the method 4000 is executed duringflight of the aircraft 22. In some of these embodiments, the GTE 10 maycorrespond to SGTE 10B, and FGTE 10A may also be mounted to the aircraft22. The method 4000 may include: operating the SGTE 10B in a low power(standby) mode of operation while fuel is supplied to the first fuelmanifold 62A and fuel supply to the second fuel manifold 62B is stopped.In some of these embodiments, the method 4000 includes operating theFGTE 10A in a high-power mode of operation while the SGTE 10B isoperated in the low power (standby) mode of operation.

Some embodiments of the method 4000 include, after fuel in the secondfuel manifold 62B is flushed into the combustor 16 and while continuingsupplying fuel to the combustor 16 by supplying fuel to the first fuelmanifold 62A, stopping supplying pressurized gas from the pressurizedgas generator 78 to the second fuel manifold 62B.

Some embodiments of the method 4000 include, after stopping supplyingpressurized gas from the pressurized gas generator 78 to the second fuelmanifold 62B and while continuing supplying fuel to the combustor 16 bysupplying fuel to the first fuel manifold 62A, initiating supplying fuelto the second fuel manifold 62B to supply fuel to the combustor 16.

Some embodiments of the method 4000 include directing supplyingpressurized gas at a location along a fuel line 76B establishing fluidcommunication between a flow divider valve 66 or 166 and the second fuelmanifold 62B.

Some embodiments of the method 4000 include, after fuel in the secondfuel manifold 62B is flushed into the combustor 16 and while supplyingfuel to the second fuel manifold 62B is stopped, continuing supplyingfuel to the combustor 16 by supplying fuel to the first fuel manifold62A.

FIG. 8 is a flowchart of a method 5000 of operating a multi-engine powerplant 42, in accordance with an embodiment. It is understood thataspects of method 5000 may be combined with other methods, or aspectsthereof, described herein. The multi-engine power plant 42 includes theFGTE 10A and the SGTE 10B drivingly connected to a common load 44.

The method 5000 includes operating the FGTE 10A and the SGTE 10B todrive the common load 44 where operating the SGTE 10B includes supplyingfuel to a combustor 16B of the SGTE 10B by supplying fuel to a firstfuel manifold 62A and a second fuel manifold 62B of the SGTE 10B (seeblock 5100).

The method 5000 includes stopping supplying fuel to the second fuelmanifold 62B of the SGTE 10B while operating the FGTE 10A and supplyingfuel to the combustor 16B of the SGTE 10B by supplying fuel to the firstfuel manifold 62A of the SGTE 10B (see block 5200).

The method 5000 includes using a pressurized gas generator 78 (e.g.,pump) to pressurize gas while operating the FGTE 10A and supplying fuelto the combustor 16B of the SGTE 10B by supplying fuel to the first fuelmanifold 62A of the SGTE 10B (see block 5300).

The method 5000 includes supplying pressurized gas from the pressurizedgas generator 78 to the second fuel manifold 62B of the SGTE 10B toflush fuel in the second fuel manifold 62B into the combustor 16B of theSGTE 10B while operating the FGTE 10A and supplying fuel to thecombustor 16B of the SGTE 10B by supplying fuel to the first fuelmanifold 62A of the SGTE 10B (see block 5400).

Some embodiments of the method 5000 include using a flow divider valve66 or 166 to stop supplying fuel to the second fuel manifold 62B and tocontinue to supply fuel to the first fuel manifold 62A.

In some embodiments of the method 5000, the common load 44 includes arotary wing of the aircraft 22. In some of these embodiments, the method5000 is executed during flight of the aircraft 22.

Some embodiments of the method 5000 include, after fuel in the secondfuel manifold 62B is flushed and while continuing supplying fuel to thecombustor 16B of the SGTE 10B by supplying fuel to the first fuelmanifold 62A, stopping supplying pressurized gas from the pressurizedgas generator 78 to the second fuel manifold 62B.

Some embodiments of the method 5000 include, after stopping supplyingpressurized gas from the pressurized gas generator 78 to the second fuelmanifold 62B and while continuing supplying fuel to the combustor 16B ofthe SGTE 10B by supplying fuel to the first fuel manifold 62A,initiating supplying fuel to the second fuel manifold 62B to resume thesupply of fuel to the combustor 16B of the SGTE 10B via the second fuelmanifold 62B.

Some embodiments of the method 5000 include directing pressurized gasinto a fuel line 76B establishing fluid communication between a flowdivider valve 66 and the second fuel manifold 62B.

Some embodiments of the method 5000 include, after fuel in the secondfuel manifold 62B is flushed and while supplying fuel to the second fuelmanifold 62B is stopped, continuing supplying fuel to the combustor 16Bof the SGTE 10B by supplying fuel to the first fuel manifold 62A.

FIG. 9 is a schematic illustration of an exemplary fuel system 350 of aGTE 10. Elements of the fuel system 350 that are similar to elements offuel systems described above are identified using like referencenumerals. The fuel system 350 includes a first (e.g., primary) fuelmanifold 62A fluidly connected to and configured to supply fuel to acombustor 16 of the GTE 10 via nozzles 61A, and a second (e.g.,secondary) fuel manifold 62B configured to supply fuel to the combustor16 via nozzles 61B. The fuel system 350 includes a flow divider assembly174 configurable (e.g., actuatable) between a first configuration and asecond configuration. The flow divider assembly 174 includes a flowdivider valve 166 and a purge valve 70. The flow divider valve 166 isconfigured to, in the first configuration, supply fuel to the first fuelmanifold 62A and the second fuel manifold 62B and to, in the secondconfiguration, stop supplying fuel to the second fuel manifold 62B whilecontinuing to supply fuel to the first fuel manifold 62A. The purgevalve 70 is configured to, in the second configuration of the flowdivider assembly 174, permit pressurized gas to flow to the second fuelmanifold 62B to flush fuel in the second fuel manifold 62B into thecombustor 16. The purge valve 70 may be configured to, in the firstconfiguration, prevent fuel from entering the gas pressure accumulator64 or the pressurized gas source 58.

In some embodiments, the fuel system 350 includes an optionalaccumulator 64 configured to, in the second configuration of the flowdivider assembly 174, supply pressurized air (or other purging gas) tothe second fuel manifold 62B to flush residual fuel in the second fuelmanifold 62B into the combustor 16.

In some embodiments, the fuel system 350 includes a (e.g., pressure orflow) regulator 68 configured to, in the second configuration of theflow divider assembly 174, control a supply of pressurized gas to theflow divider valve 166 to maintain a controlled fuel flow rate to thecombustor 16 via the second fuel manifold 62B below a threshold whenfuel is being flushed into the combustor 16 to prevent the delivery of afuel spike to the combustor 16 or to limit the magnitude of such fuelspike.

In some embodiments, either or both at engine shutdown and transitioningto low-power operation, the fuel system 350 may enable flow and/orpressure regulation of the purge gas so that fuel purged out of the fuelmanifolds 62A or 62B enters the combustor 16 at a controlled flow rateto prevent a sudden acceleration of gas turbine engine 10.

In some embodiments, the fuel system 350 may be engine mounted,partially engine mounted or remotely mounted. The purge valve 70 may beintegral to (e.g., in unitary construction with) the flow divider valve166, or may be integral to (e.g., in unitary construction with) theaccumulator 64, or may be separate. In some embodiments, the regulator68 may be integral to (e.g., in unitary construction with) the flowdivider valve 166, or may be integral to (e.g., in unitary constructionwith) the accumulator 64, or may be separate. In some embodiments, thegas pressure and/or the gas flow regulation or non-regulation may beapplied to one or several manifolds 62A, 62B dependently orindependently form each other. In some embodiments, the pressureregulator 168 may be integral to (e.g., in unitary construction with)the accumulator 64 or may be separate. In some embodiments, purging thefuel manifold(s) 62A, 62B may be maintained continuously over a longperiod of time during which an aircraft engine is operated, or may beterminated once the fuel manifold(s) 62A, 62B and associated nozzles61A, 61B are considered empty of fuel. In some embodiments, differentpressure sources may be used to purge the different fuel manifolds 62A,62B. In some embodiments, the fuel manifolds 62A, 62B may have common,partially common or completely independent fuel purging systems.

In some embodiments, the fuel system 350 includes a pressure regulator168 to regulate the pressure of pressurized air (or other gas) flowingto the accumulator 64 from the pressurized gas source 58. The pressureregulator 168 may be used to regulate desired charge pressure in theaccumulator 64.

The flow divider valve 166 and/or flow divider assembly 174 may compriseone or more embodiments of (flow divider) valves, or assemblies,described herein, such as embodiments described in FIGS. 16-25C.

FIG. 10 is a flowchart of another exemplary method 6000 of operating aGTE 10. It is understood that aspects of method 6000 may be combinedwith other methods, or aspects thereof, described herein. The GTE 10includes a first fuel manifold 62A and a second fuel manifold 62Bfluidly connected to and configured to supply fuel to a combustor 16 ofthe GTE 10. The method 6000 includes supplying fuel to the combustor 16by supplying fuel to the first and second fuel manifolds 62A, 62B usinga common flow divider valve 166 (block 6100). The method 6000 alsoincludes stopping supplying fuel to the second fuel manifold 62B whilesupplying fuel to the combustor 16 by supplying fuel to the first fuelmanifold 62A (block 6200), and supplying pressurized gas to the secondfuel manifold 62B via the flow divider valve 166 to flush fuel in thesecond fuel manifold 62B into the combustor 16 while supplying fuel tothe combustor 16 by supplying fuel to the first fuel manifold 62A (block6300).

Some embodiments of the method 6000 include discharging pressurized air(or other gas) from the accumulator 64 into the second fuel manifold 62Bvia the flow divider valve 166 to flush fuel in the second fuel manifold62B into the combustor 16.

In some embodiments of the method 6000, stopping supplying fuel to thesecond fuel manifold 62B causes an increase in fuel flow to the firstfuel manifold 62A by restricting fuel flow to the second fuel manifold62B using the flow divider valve 166.

In some embodiments of the method 6000, the GTE 10 is mounted to anaircraft 22. In some of these embodiments, the method 6000 is executedduring flight of the aircraft 22.

Some embodiments of the method 6000 include, when fuel is being flushedinto the combustor 16, maintaining a fuel flow rate to the combustor 16via the second fuel manifold 62B below a threshold by controlling asupply of pressurized gas to the second fuel manifold 62B to prevent thedelivery of a fuel spike to the combustor 16 during purging or to limitthe magnitude of such fuel spike.

Some embodiments of the method 6000 include, after fuel in the secondfuel manifold 62B is flushed into the combustor 16 and while supplyingfuel to the combustor 16 via the second fuel manifold 62B is stopped,continuing to supply fuel to the combustor 16 via the first fuelmanifold 62A using the flow divider valve 166.

Some embodiments of the method 6000 include charging the accumulator 64using pressurized air from a compressor section 14 of the GTE 10 priorto stopping supplying fuel to the second fuel manifold 62B.

In some embodiments of the method 6000, while supplying fuel to thecombustor 16 by supplying fuel to the first fuel manifold 62A via thecommon flow divider valve 166, stopping supplying fuel to the secondfuel manifold 62B may include stopping supplying fuel to the second fuelmanifold 62B via the common flow divider valve 166.

FIG. 11 is a flowchart of another exemplary method 6050 of operating aGTE 10. It is understood that aspects of method 6050 may be combinedwith other methods, or aspects thereof, described herein. In someembodiments, method 6050 may be an exemplary method to be carried outduring low-power (e.g., standby) operation or shutdown of the GTE 10. Insome embodiments, the method 6050 may allow the engine to be lit as longas possible during shut-down to burn residual fuel in the combustor 16and/or one or more of the fuel manifolds 62A, 62B.

The method 6050 includes supplying fuel to the combustor 16 by supplyingfuel to one or more of the fuel manifolds 62A, 62B (block 6150), andstopping supplying fuel to the one or more of the fuel manifolds 62A,62B (block 6250). The method 6050 also includes supplying pressurizedgas to the one or more of the fuel manifolds 62A, 62B to flush residualfuel into the one or more of the fuel manifolds 62A, 62B into thecombustor 16; and maintaining a fuel flow rate to the combustor 16 viathe one or more of the fuel manifolds 62A, 62B below a threshold byregulating the pressurized gas supplied to the one or more of the fuelmanifolds 62A, 62B (block 6350).

Method 6050 may be performed for some or all fuel manifolds 62A, 62B ofthe GTE 10 depending on whether the GTE 10 is transitioning from ahigh-power operating regime to a low power operating regime, or the GTE10A (or 10B) is being shut down.

FIG. 12 is a flowchart of another exemplary method 7000 of operating amulti-engine power plant 42 of an aircraft 22. It is understood thataspects of method 7000 may be combined with other methods, or aspectsthereof, described herein. The multi-engine power plant 42 includes theFGTE 10A and the SGTE 10B. The FGTE 10A and SGTE 10B are drivinglyconnected to a common load 44.

The method 7000 includes operating the FGTE 10A and the SGTE 10B todrive the common load 44. Operating the SGTE 10B includes supplying fuelto a combustor 16B of the SGTE 10B by supplying fuel to a first fuelmanifold 62A and a second fuel manifold 62B of the SGTE 10B via a commonflow divider valve 166 (block 7100). The method 7000 also includesstopping supplying fuel to the second fuel manifold 62B of the SGTE 10Bwhile operating the FGTE 10A and supplying fuel to the combustor 16B ofthe SGTE 10B by supplying fuel to the first fuel manifold 62A of theSGTE 10B (block 7200). The method 7000 includes supplying pressurizedgas to the second fuel manifold 62B of the SGTE 10B via the flow dividervalve 166 to flush fuel in the second fuel manifold 62B into thecombustor 16B of the SGTE 10B while operating the FGTE 10A and supplyingfuel to the combustor 16B of the SGTE 10B by supplying fuel to the firstfuel manifold 62A of the SGTE 10B (block 7300).

Some embodiments of the method 7000 include discharging pressurized air(or other gas) from an accumulator 64 into the second fuel manifold 62Bto flush fuel in the second fuel manifold 62B into the combustor 16B ofthe SGTE 10B.

In some embodiments of the method 7000, the common load 44 includes arotary wing of the aircraft 22 and the method is executed during flightof the aircraft 22.

Some embodiments of the method 7000 include, when fuel is being flushedinto the combustor 16B of the SGTE 10B, maintaining a fuel flow rate tothe combustor 16B via the second fuel manifold 62B below a threshold bycontrolling a supply of pressurized gas to the second fuel manifold 62B.

Some embodiments of the method 7000 include, after fuel in the secondfuel manifold 62B is flushed into the combustor 16B of the SGTE 10B andwhile supplying fuel to the combustor 16B via the second fuel manifold62B is stopped, continuing to supply fuel to the combustor 16B via thefirst fuel manifold 62A using the flow divider valve 166.

Some embodiments of the method 7000 include charging the accumulator 64using pressurized air from a compressor section 14 of the multi-enginepower plant 42.

Some embodiments of the method 7000 include charging the accumulator 64using pressurized air from a compressor section 14A, 14B of themulti-engine power plant 42 prior to stopping supplying fuel to thesecond fuel manifold 62B.

In some embodiments of the method 7000, while operating the FGTE 10A andsupplying fuel to the combustor 16 of the SGTE 10B by supplying fuel tothe first fuel manifold 62A of the SGTE 10B: stopping supplying fuel tothe second fuel manifold 62B of the SGTE 10B includes while supplyingfuel to the combustor 16 of the SGTE 10B by supplying fuel to the firstfuel manifold 62A of the SGTE 10B via the common flow divider valve 166,stopping supplying fuel to the second fuel manifold 62B of the SGTE 10Bvia the common flow divider valve 166.

FIG. 13 is a schematic illustration of another exemplary fuel system 450of a GTE 10. Elements of the fuel system 450 that are similar toelements of fuel systems described above are identified using likereference numerals. The fuel system 450 may include two or more fuelmanifolds (e.g., 62A-62D) fluidly connected to and configured to supplyfuel to a combustor 16 of the GTE 10. The fuel system 450 may supplyeach of the fuel manifolds 62A-62D via a respective/separate flowdivider valve 166A-166D forming part of a flow divider assembly 274. Thefuel system 450 may also supply fuel to the one or more of the fuelmanifolds 62A-62D via a common flow divider valve. Flow divider valves166A-166D may be designed to open or close (i.e. supply fuel or stopsupplying fuel to one or more of the fuel manifold 62A-62D). In someembodiments, fuel may be supplied or stopped according to apredetermined schedule (e.g. dependent on inlet fuel flow rate or fuelpressure, or fuel flow rate or fuel pressure in one or more of the fuelmanifolds 62A-62D). Flow divider valves 166A-166D may provide a functionof flow division. In some embodiments, one or more flow divider valves166A-166D may each comprise a single valve. In some embodiments, one ormore flow divider assemblies may each comprise a plurality of flowdivider valves 166A-166D. In some embodiments described herein, the flowdivider valves may be spool-type valves. In some embodiments describedherein, the flow divider valves may be poppet-type valves.

In particular, the fuel system 450 includes a first fuel manifold 62Aand a second fuel manifold 62B configured to supply fuel to thecombustor 16. The flow divider assembly 274 is configurable (e.g.,actuatable) between a first configuration and a second configuration.The first flow divider valve 166A is configured to, in the first andsecond configurations, supply fuel to the first fuel manifold 62A. Thesecond flow divider valve 166B is configured to, in the firstconfiguration, supply fuel to the second fuel manifold 62B and to, inthe second configuration, stop supplying fuel to the second fuelmanifold 62B. The flow divider assembly 274 includes a purge valve 70Bconfigured to, in the second configuration, permit pressurized gas toflow to the second fuel manifold 62B via the second flow divider valve166B to flush residual fuel in the second fuel manifold 62B into thecombustor 16. In some embodiments, the purge valve 70B may be configuredto, in the first configuration, prevent fuel from flowing to and/orentering the pressurized gas source 58A. In some embodiments, the flowdivider assembly 274 includes an additional purge valve 70A configuredto control flow of purging gas to the first fuel manifold 62A.

In some embodiments of the fuel system 450, the purge valve 70B and thefirst and second flow divider valves 166A, 166B are disposed inside acommon housing 82. In some embodiments, the common housing 82 includesthe plurality of flow divider valves 166A-166D. The common housing 82may include one or more fuel inlets 84 (ports) configured to supply fuelto the first and second flow divider valves 166A, 166B, and in someembodiments additional flow divider valves 166C, 166D. The commonhousing 82 may include one or more pressurized gas inlets 86B configuredto supply pressurized gas to the second flow divider valve 166B. In someembodiments, the common housing 82 may include additional pressurizedgas inlets 86A and 86C to supply pressurized gas to the flow dividervalves 166A, 166C, 166D. In some embodiments, the pressurized gas inlets86A-86C (ports) may supply pressurized gas to fuel manifold 62A-62D viaflow divider valves 166A-166D to flush fuel in the fuel manifold62A-62D. The common housing 82 may include one or more outlets 88A, 88B(ports) configured to allow fluid communication between the first flowdivider valve 166A and the first fuel manifold 62A, and between thesecond flow divider valve 166B and the second fuel manifold 62B. In someembodiments, the common housing 82 may include one or more additionaloutlets 88C, 88D configured to allow fluid communication between theflow divider valves 166C, 166D and the respective fuel manifolds 62C,62D.

The common housing 82 may include any suitable enclosure made frommetallic, polymeric and/or composite material, for example, for housingonly components of the fuel system 450 or of other fuel system(s)described herein. The common housing 82 may permit the components of theflow divider assembly 274 to be preassembled and installed into (orremoved from) the GTE 10 as a unit. In some embodiments, the commonhousing 82 may include a common support platform onto which componentsthe flow divider assembly 274 may be preassembled and installed into (orremoved from) the GTE 10 as a unit. In some embodiments of the fuelsystem 450, the common housing 82 could be replaced by such commonplatform. The use of the common housing 82 and/or the common supportplatform may facilitate the assembly, installation, removal andmaintenance of the flow divider assembly 274. Alternatively, in someembodiments, the components of the flow divider assembly 274 couldinstead be separately installed into the GTE 10 without the use of acommon housing 82 or a common support platform.

In various embodiments of the fuel system 450, the first and second fuelmanifolds may be any two of the fuel manifolds 62A-62D, and the firstand second flow divider valves may be any two of the flow divider valves166A-166D.

In some embodiments of the fuel system 450, flow divider valves166A-166D may be in fluid communication with the combustor 16 by way ofa parallel arrangement between the fuel inlet(s) 84 and the fuel outlets88A-88D.

Some embodiments of the fuel system 450 include one or more regulators68 disposed in the common housing 82 and configured to receivepressurized gas via one or more of the pressurized gas inlets 86A-86C.The regulator(s) 68 may be configured to, in the second configuration ofthe flow divider assembly 274, control a supply of pressurized gas tothe second flow divider valve 166B to maintain a fuel flow rate to thecombustor 16 via the second fuel manifold 62B below a threshold, whenfuel is being flushed into the combustor 16 to prevent the delivery of afuel spike to the combustor 16 during purging or to limit the magnitudeof such fuel spike.

Some embodiments of the fuel system 450 include a calibrated orifice 80to restrict pressurized gas flow to one or more of the flow dividervalve 166A-166D. The calibrated orifice 80 may be disposed inside thecommon housing 82 and configured to receive pressurized gas via one ormore of the pressurized gas inlets 86A-86C.

Some embodiments of the fuel system 450 include a third fuel manifold62C configured to supply fuel to the combustor 16 and a third flowdivider valve 166C configured to, in the first configuration, supplyfuel to the third fuel manifold 62C and to, in the second configurationof the flow divider assembly 274, stop supplying fuel to the third fuelmanifold 62C. The purge valve 70B is configured to, in the secondconfiguration of the flow divider assembly 274, permit pressurized gasto flow to the third fuel manifold 62C via the third flow divider valve166C to flush fuel in the third fuel manifold 62C into the combustor 16.The purge valve 70B, in the second configuration of the flow dividerassembly 274, may fluidly connect a pressurized gas source 58 to thethird fuel manifold 62C to supply pressurized gas to the third fuelmanifold 62C via the third flow divider valve 166C to flush fuel in thethird fuel manifold 62C into the combustor 16. The purge valve 70B maysimultaneously cause pressurized gas flow to both second and third fuelmanifold 62B, 62C via the second and third flow divider valves 166B,166C respectively.

The pressurized gas inlets 86A-86C may receive pressurized gas from acommon or different pressurized gas sources 58A and 58B. In someembodiments, the pressurized gas sources 58A-58B may be compressorsections 14, 14A, 14B of any gas turbine engine 10A, 10B of themulti-engine power plant 42 (shown in FIG. 1), or one or more othersources (e.g., accumulator, reservoir, pump).

In some configurations of the flow divider assembly 274, the pressurizedgas sources 58A and 58B may be used for purging some or all of the fuelmanifolds 62A-62D of residual fuel via the flow divider valves166A-166D.

In some embodiments, the fuel system 450 can be used to purge a fuelmanifold 62A (or one of 62B-62D) or several fuel manifolds (a subset oftwo or more fuel manifolds 62A-62D) sequentially or simultaneously bymeans of purge valve(s) 70A-70C. In various embodiments, there may be apurge valve for each fuel manifold 62A-62D, or two or more fuelmanifolds 62A-62D may share a same purge valve. In some embodiments,purge valves 70A-70C may be housed in the common housing 82.

When purging the fuel manifolds 62A-62D and associated fuel nozzles (notshown in FIG. 13), the purging gas pressure and/or flow into the fuelmanifold(s) may be regulated, and/or may be limited by a calibratedorifice or other flow restriction. In some embodiments, regulating(pressurized) gas pressure and/or flow-rate delivered to the fuelmanifold(s) 62A-62D during purging may prevent undesirable fuel spikes,and provide more even delivery of purged fuel into the combustor 16 overtime. Pressure and/or flow regulators may be housed in the commonhousing 82. In some embodiments, purge valves 70A-70C may function aspressure and/or flow regulators. Orifices or restrictions 80 and/or maybe located upstream or downstream of one or more purge valves (e.g.purge valves 70A, 70B), or can be integral to (e.g., unitaryconstruction with) the one or more purge valves.

In some embodiments, the fuel system 450 may allow staged purging of thefuel manifolds 62A-62D to prevent flame out of the combustor 16 duringthe purge, e.g. including preventing white smoke resulting from anincomplete fuel burn. In various embodiments, common or distinctpressurized gas sources 58A-58B to purge various subsets of fuelmanifolds 62A-62D. Timing or staging of the purge of each fuel manifold62A-62D may allow purging one or more (or all) of the fuel manifolds62A-62D while keeping a combustor flame on/alive, e.g. such that all thefuel from the fuel manifolds 62A-62D is burnt/combusted completelyinstead of being vaporized to thereby avoid white smoke.

In various embodiments, a common pressurized gas source 58A or 58B maybe used to purge several fuel manifolds 62A-62D via the flow dividerassembly 274, simultaneously or sequentially. Alternatively differentpressurized gas sources 58A, 58B may be used to purge different fuelmanifolds 62A-62D via the flow divider assembly 274, simultaneously orsequentially. In various embodiments, the fuel system 450 may be used toenter a specific (e.g., low-power) mode of operation for the engine, ormay be used at shut down.

FIG. 14 is a flowchart of another exemplary method 8000 of operating aGTE 10. It is understood that aspects of method 8000 may be combinedwith other methods, or aspects thereof, described herein. The GTE 10includes a first fuel manifold 62A and a second fuel manifold 62Bfluidly connected to and configured to supply fuel to a combustor 16 ofthe GTE 10. The method 8000 includes supplying fuel to the combustor 16by supplying fuel to the first fuel manifold 62A via the first flowdivider valve 166A, and supplying fuel to the second fuel manifold 62Bvia the second flow divider valve 166B (block 8100). The method alsoincludes stopping supplying fuel to the second fuel manifold 62B whilesupplying fuel to the combustor 16 by supplying fuel to the first fuelmanifold 62A (block 8200), and supplying pressurized gas to the secondfuel manifold 62B via the second flow divider valve 166B to flushresidual fuel in the second fuel manifold 62B into the combustor 16while supplying fuel to the combustor 16 by supplying fuel to the firstfuel manifold 62A (block 8300).

In some embodiments of the method 8000, the GTE 10 has a third fuelmanifold 62C (or 62D). Some of these embodiments include, whilesupplying fuel to the first and second fuel manifolds 62A, 62B,supplying fuel to the combustor 16 by supplying fuel to the third fuelmanifold 62C via a third flow divider valve 166C, and while supplyingfuel to the first fuel manifold 62A and to the second fuel manifold 62B,stopping supplying fuel to the third fuel manifold 62C, and supplyingpressurized gas to the third fuel manifold 62C via the third flowdivider valve 166C to flush residual fuel in the third fuel manifold 62Cinto the combustor 16. Supplying pressurized gas to the third fuelmanifold 62C may include opening a purge valve 70B permittingpressurized gas flow into the third flow divider valve 166C.

Some embodiments of the method 8000 include, after fuel in the thirdfuel manifold 62C is flushed into the combustor 16 and while supplyingfuel to the second and third fuel manifolds 62B, 62C is stopped,continuing to supply fuel to the combustor 16 by supplying fuel to thefirst fuel manifold 62A via the first flow divider valve 166A. Such amethod may be carried out during low power standby mode of operation ofthe multi-engine power plant 42 of the aircraft 22 during a sustainedcruise regime of flight.

In some embodiments of the method 8000, supplying pressurized gas to thesecond fuel manifold 62B via the second flow divider valve 166B includesopening the purge valve 70B. In some of these embodiments, purging orflushing fuel from second and third fuel manifolds 62B and 62C may becontrolled or initiated by the opening of purge valve 70B. In someembodiments of the method 8000, an additional purge valve 70A may beprovided to control purging or flushing of residual fuel from the firstfuel manifold 62A during shut-down of the GTE 10 for example.

In some embodiments of the method 8000, the GTE 10 is mounted to anaircraft 22. In some of these embodiments, the method 8000 is executedduring flight of the aircraft 22.

In some embodiments of the method 8000, the GTE 10 is one of two or moreGTEs 10A, 10B mounted to the aircraft 22. In some embodiments, themethod 8000 includes: operating the SGTE 10B in a low power mode ofoperation while fuel is supplied to the first fuel manifold 62A of theSGTE 10B and fuel supply to the second fuel manifold 62B of the SGTE 10Bis stopped; and operating the FGTE 10A in a high-power mode of operationwhile the SGTE 10B is operated in the low power mode of operation.

Some embodiments of the method 8000 include, when fuel is being flushedinto the combustor 16, maintaining a fuel flow rate to the combustor 16via the second fuel manifold 62B below a threshold by controlling asupply of pressurized gas to the second fuel manifold 62B to prevent thedelivery of a fuel spike to the combustor 16 during purging or to limitthe magnitude of such fuel spike.

Some embodiments of the method 8000 include using a calibrated orifice80 to restrict pressurized gas flow to the second fuel manifold 62Band/or any fuel manifolds 62A-62D of GTE 10.

Some embodiments of the method 8000 include, after fuel in the secondfuel manifold 62B is flushed into the combustor 16 and while supplyingfuel to the combustor 16 via the second fuel manifold 62B is stopped,continuing to supply fuel to the combustor 16 by supplying fuel to thefirst fuel manifold 62A via the first flow divider valve 166A.

FIG. 15 is a flowchart of another exemplary method 9000 of operating amulti-engine power plant 42. It is understood that aspects of method9000 may be combined with other methods, or aspects thereof, describedherein. The multi-engine power plant 42 includes the FGTE 10A and theSGTE 10B, the FGTE 10A and SGTE 10B being drivingly connected to acommon load 44.

The method 9000 includes operating the FGTE 10A and the SGTE 10B todrive the common load 44. Operating the SGTE 10B includes: supplyingfuel to a combustor 16B of the SGTE 10B by supplying fuel to a firstfuel manifold 62A of the SGTE 10B via a first flow divider valve 166A;and supplying fuel to the combustor 16B by supplying fuel to a secondfuel manifold 62B of the SGTE 10B via a second flow divider valve 166B(block 9100). The method 9000 also includes stopping supplying fuel tothe second fuel manifold 62B of the SGTE 10B while operating the FGTE10A and supplying fuel to the combustor 16B of the SGTE 10B by supplyingfuel to the first fuel manifold 62A of the SGTE 10B (block 9200), andsupplying pressurized gas to the second fuel manifold 62B of the SGTE10B via the second flow divider valve 166B to flush fuel in the secondfuel manifold 62B into the combustor 16B of the SGTE 10B while operatingthe FGTE 10A and supplying fuel to the combustor 16B of the SGTE 10B bysupplying fuel to the first fuel manifold 62A of the SGTE 10B (block9300).

In some embodiments of the method 9000, the common load 44 includes arotary wing of the aircraft 22. In some of these embodiments, the method9000 is executed during flight of the aircraft 22.

Some embodiments of the method 9000 include, when fuel is being flushedinto the combustor 16B of the SGTE 10B, maintaining a fuel flow rate tothe combustor 16B via the second fuel manifold 62B below a threshold bycontrolling a supply of pressurized gas to the second fuel manifold 62Bto prevent the delivery of a fuel spike to the combustor 16B duringpurging or limit the magnitude of such fuel spike.

Some embodiments of the method 9000 include using a calibrated orifice80 to restrict pressurized gas flowing to the second fuel manifold 62B.Some embodiments of the method 9000 include using a calibrated orifice80 to restrict pressurized gas flow to any fuel manifolds 62A-62D of themulti-engine power plant 42. Some embodiments of the method 9000 includeusing one or more flow and/or pressure regulator(s) to control purginggas delivery to one or more fuel manifolds 62A-62D of the multi-enginepower plant 42.

Some embodiments of the method 9000 include, after fuel in the secondfuel manifold 62B is flushed into the combustor 16B of the SGTE 10B andwhile supplying fuel to the second fuel manifold 62B is stopped,continuing supplying fuel to the combustor 16B by supplying fuel to thefirst fuel manifold 62A.

FIG. 16 is a schematic cross-sectional view of another exemplary fuelsystem 550 of a GTE 10. Elements of the fuel system 550 that are similarto elements of fuel systems described above are identified using likereference numerals. The fuel system 550 includes fuel manifolds 62A-62Cfluidly connected to and configured to supply fuel to a combustor 16 ofthe GTE 10. The fuel system 550 includes a flow divider assembly 374configurable (e.g., actuatable) between a first configuration and asecond configuration. The flow divider assembly 374 may be configurable(e.g., actuatable) to adopt additional configurations. The flow dividerassembly 374 may include a first flow divider valve 366A configured to,in the first and second configurations, supply fuel to the first fuelmanifold 62A, a second flow divider valve 366B configured to, in thefirst configuration, supply fuel to the second fuel manifold 62B and to,in the second configuration, stop supplying fuel to the second fuelmanifold 62B.

In some embodiments, the flow divider assembly 374 may include the firstflow divider valve 366A which, in the first and second configurations,is fluidly connected to the first fuel manifold 62A and configured tosupply fuel to the first fuel manifold 62A. In some embodiments, theflow divider assembly 374 may include the second flow divider valve366B. In the first configuration of the flow divider assembly 374, thesecond flow divider valve 366B may be fluidly connected to the secondfuel manifold 62B and may be configured to supply fuel to the secondfuel manifold 62B and, in the second configuration, may be configured tostop supplying fuel to the second fuel manifold 62B.

Spool 399B of the second flow divider valve 366B may serve as a purgevalve configured to, in the second configuration, permit pressurized gasto flow to the second fuel manifold 62B via the second flow dividervalve 366B to flush fuel in the second fuel manifold 62B into thecombustor 16. The purge valve may, in the second configuration of theflow divider assembly 374, fluidly connect a pressurized gas source tothe second fuel manifold 62B to supply pressurized gas to the secondfuel manifold 62B via the second flow divider valve 366B to flush fuelin the second fuel manifold 62B into the combustor 16. The flow dividerassembly 374 may be housed in a common housing 182 including a (main)fuel inlet 184, one or more pressurized gas inlets 186A-186C, one ormore outlets 188A-1880, and one or more flow divider valves 366A-366Cdisposed inside of the common housing 182. Some embodiments of the fuelsystem 550 may have fewer or more flow divider valves than illustrated.Seals may be provided in the flow divider valve assembly 374 to preventleakage.

The flow divider valves 366A-366C may be spool valves configured to beresponsive to the fuel pressure at a main fuel inlet 184. Each of theflow divider valves 366A-366C may include an outlet 394A-394C and a fuelinlet 390A-390C. The spools 383A-383C may serve as fuel valves foropening and closing fuel inlets 390A-390C and outlets 394A-394C. Thespools 399A-399C may define pressurized gas inlet (purging) valves foropening and closing pressurizing gas inlets 392A-392C. The spools399A-399C and their associated spools 383A-3830 may respectively beinter-connected by (e.g., coil) springs (shown in circle/oval-dottedlines). The spools 399A-399C and 383A-383C may be responsive topressure, and may be actuatable solely hydraulically. The spools399A-399C and their associated spools 392A-392C may be coaxial andactuatable along a common orientation.

The first flow divider valve 366A may be configured to, when the fuelpressure is above a first cracking (i.e., opening) pressure of the firstflow divider valve 366A, open the fuel inlet 390A of the first flowdivider valve 366A to receive fuel via the main fuel inlet 184 and to,when the fuel pressure is below the first cracking pressure of the firstflow divider valve 366A, close the fuel inlet 390A of the first flowdivider valve 366A and open a pressurized gas inlet 392A for purging thefirst fuel manifold 62A.

The second flow divider valve 366B may be configured to, when the fuelpressure is above the first cracking pressure of the first flow dividervalve 366A and also above a second cracking pressure of the second flowdivider valve 366B, open the fuel inlet 390B of the second flow dividervalve 366B to receive fuel via the fuel outlet 394A of the first flowdivider valve 366A, and to, when the fuel pressure is below the secondcracking pressure of the second flow divider valve 366B, close the fuelinlet 390B of the second flow divider valve 366B and open a pressurizedgas inlet 392B for purging the second fuel manifold 62B. The third flowdivider valve 366C associated with the third fuel manifold 62C may beconfigured similarly to the second flow divider valve 366B and the firstflow divider valve 366A. In some embodiments, the fuel inlet 390B of thesecond flow divider valve 366B may be connected to the main fuel inlet184.

The cracking pressures of the flow divider valves 366A-366C may bepredetermined characteristics of the flow divider valves 366A-366C. Insome embodiments, the springs provide resistance to movement of thespools 383A-383C and 399A-399C of the respective flow divider valves366A-366C and may be selected to define the respective crackingpressures. Exemplary relative stiffnesses of the springs are illustratedin FIG. 16 by larger circles/ovals/broken lines representing a higherstiffness and smaller circles/ovals/broken lines representing a lowerstiffness. The movement of the spools 399A-399C to release pressurizedgas in the respective manifolds 62A-62C may be caused by respectivepressures of the pressurized gas at the respective gas inlets 392A-392C.One or more purge valves (not shown in FIG. 16) may be included in thesystem 550 upstream of the gas inlets 392A-392C.

FIG. 16 shows the spool 383A of the first flow divider valve 366Apositioned to permit fuel flow to the first fuel manifold 62A, and thespool 399A positioned to prevent pressurized gas from being delivered tothe first fuel manifold 62A and, in some embodiments, to prevent fuelflow toward a pressurized gas source. FIG. 16 shows the spool 383B ofthe second flow divider valve 366B positioned to prevent fuel flow tothe second fuel manifold 62B, and the spool 399B positioned to permitthe supply of pressurized gas to the second fuel manifold 62B. FIG. 16shows the spool 383C of the third flow divider valve 366C positioned toprevent fuel flow to the third fuel manifold 62C, and the spool 399Cpositioned to permit the supply of pressurized gas to the third fuelmanifold 62C.

In reference to FIG. 16, the flow divider valves 366A-366B may beoperatively disposed in series with respect to fuel distribution. Forexample, the fuel from the fuel inlet 184 may flow through the firstflow divider valve 366A before reaching the second flow divider valve366B, and the fuel may flow through the second flow divider valve 366Bbefore reaching the third flow divider valve 366C. Accordingly, a lowerfuel delivery pressure at the fuel inlet 184 may cause only flow dividervalve 366A to open so that only fuel manifold 62A is supplied with fuel.A medium fuel delivery pressure at the fuel inlet 184 may cause bothflow divider valves 366A and 366B to open so that both fuel manifolds62A and 62B are supplied with fuel. A higher fuel delivery pressure atthe fuel inlet 184 may cause all three flow divider valves 366A-366C toopen so that all three fuel manifolds 62A-62C are supplied with fuel.

In some embodiments, the flow divider valves 366A-366B may beoperatively disposed in parallel with respect to fuel distribution. Forexample, the fuel from the fuel inlet 184 may flow simultaneously toeach of the fuel manifolds 62A-62C via the respective flow dividervalves 366A-366C arranged in parallel and having different crackingpressures. Accordingly, a first (e.g., high) fuel delivery pressure atthe fuel inlet 184 may cause a first set of the flow divider valves366A-366C to open and allow the associated one or more of the fuelmanifolds (e.g., 62A-62C) to be supplied with fuel. Similarly, a second(e.g., low) fuel delivery pressure at the fuel inlet 184 may cause asecond different set of the flow divider valves 366A-366C to open andallow the associated one or more of the fuel manifolds (e.g., only 62Aor only 62A and 62B) to be supplied with fuel.

In reference to FIGS. 14 and 16, an embodiment of method 8000 mayinclude supplying fuel to the combustor 16 by supplying fuel to thefirst fuel manifold 62A via the first flow divider valve 366A, andsupplying fuel to the second fuel manifold 62B via the second flowdivider valve 366B. While supplying fuel to the combustor 16 bysupplying fuel to the first fuel manifold 62A, method 8000 may includestopping supplying fuel to the second fuel manifold 62B, and supplyingpressurized gas to the second fuel manifold 62B via the second flowdivider valve 366B to flush fuel in the second fuel manifold 62B intothe combustor 16.

In some embodiments of the method 8000, the first and second flowdivider valves 366A, 366B may be spool-type valves.

In some embodiments of the method 8000, supplying fuel to the combustor16 by supplying fuel to the first fuel manifold 62A via the first flowdivider valve 366A and supplying fuel to the second fuel manifold 62Bvia the second flow divider valve 366B may include supplying fuel to thefuel inlet 390A of the first flow divider valve 366A via the main fuelinlet 184, using the outlet 394A of the first flow divider valve 366A tosupply fuel to the first fuel manifold 62A, supplying fuel to the fuelinlet 390B of the second flow divider valve 366B via the outlet 394A ofthe first flow divider valve 366A, and using the outlet 394B of thesecond flow divider valve 366B to supply fuel to the second fuelmanifold 62B.

When supplying fuel to the first fuel manifold 62A and to the secondfuel manifold 62B via the main fuel inlet 184, the method 8000 mayinclude reducing fuel delivery pressure at the main fuel inlet 184 tobetween the first cracking pressure of the first flow divider valve 366Aand the second cracking pressure of the second flow divider valve 366Bto cause the spool 383B to close the fuel inlet 390B of the second flowdivider valve 366B and thereby stop supplying fuel to the second fuelmanifold 62B. Such closing actuation of the spool 383B may automaticallyallow the spool 399B of the second flow divider valve 366B to also move(due to the pressure of the pressurized gas and to the spring force) andestablish fluid communication between the pressurizing gas inlet 392Band the outlet 394B in order to supply pressurized gas to the secondfuel manifold 62B and flush residual fuel in the second fuel manifold62B into the combustor 16.

In some embodiments, one or more portions of flow divider valves366A-366C may be in fluid communication with a lower pressure source inorder to prevent pressure equalization between two sides of a spool ofthe valves 366A-366C, e.g. due to lap leakages between the valve spooland bore, and/or to avoid a side of the valve (e.g. the back of thevalve and/or the spring chamber of the valve) to build up pressure whenthe spool is moving (e.g. retracting) and the spring is deforming (e.g.compressing axially). A lower pressure source may be a fuel tank, or ainlet of a fuel control unit, or any location of the fuel system at alower pressure than the inlet 390A-390C of the flow divider valve366A-366C.

In some embodiments, the flow divider valve assembly 374 may comprisetwo or more (e.g., flow divider) valves 366A-366C in a common housing182 and positively isolated from each other when one or more of the fuelmanifolds 62A-62C are shut off and purged empty from fuel by purging gasduring engine operation or at engine shut down. The flow divider valves366A-366C may positively seal the fuel manifolds 62A-62C from oneanother to stop or mitigate fuel leakages from a fuel manifoldcontaining fuel to another manifold empty of fuel. In variousembodiments, the fuel manifolds 62A-62C may be kept sealed from oneanother by using soft seats, hard seats, dynamic seals, air seals or anyother type of seal and/or by using any combination of such or otherseals in the flow divider valve assembly 374.

In some embodiments, when one or more of the flow divider valves366A-366C are connected to a purging pressurized gas source and are in aconfiguration that enables purging the associated fuel manifolds62A-62C, the fuel system 550 may be configured to prevent or mitigate(e.g. limit) pressurized purging gas from flowing toward the lowerpressure source by means of a check valve, fuse, seal, fixed meteringorifice, variable orifice, or any other suitable device. In somesituations, purging leaked fuel from a fuel manifold containing fuel toanother manifold empty of fuel may be conducted using the purging gas ona continuous basis or intermittently.

In various embodiments, an electrically controlled active system whichcontrols and regulates the pressurized purge gas flow to each of thefuel manifolds 62A-62C may be used instead. Fuel flow from an upstreamflow divider (e.g. flow divider valve 366A or 366B) valve to adownstream flow divider valve (e.g. respectively, flow divider valve366B or 366C) may be shut off by means of a solenoid valve or otherelectrically controlled active system or a mechanical isolating valve toeliminate or mitigate risk of fuel leakage between fuel manifolds.

FIGS. 17A-17C are schematic cross-sectional views of an embodiment of aflow divider valve 466 (which may be part of a flow divider assembly474) for a fuel system 50 (or other fuel system) in, respectively, afirst configuration (FIG. 17A), a second configuration (FIG. 17B), and athird configuration (FIG. 17C).

FIGS. 18A-18C are schematic cross-sectional views of another embodimentof a flow divider valve 566 (which may be part of a flow dividerassembly 574) for a fuel system 50 (or other fuel system) in,respectively, a first configuration (FIG. 18A), a second configuration(FIG. 18B), and a third configuration (FIG. 18C).

FIGS. 19A-19D are schematic cross-sectional views of another embodimentof a flow divider valve 666 (which may be part of a flow dividerassembly 674) for a fuel system 50 (or other fuel system) in,respectively, a first configuration (FIG. 19A), a second configuration(FIG. 19B), a third configuration (FIG. 19C), and a fourth configuration(FIG. 19D). Like the first configuration, the fourth configuration ofFIG. 19D may cause fuel to be supplied to both fuel manifolds 62A, 62Bbut fuel flow to the second manifold 62B via passage 699 may be at areduced flow rate compared to the first configuration of FIG. 19A.

FIGS. 20A-20C are schematic cross-sectional views of another embodimentof a flow divider valve 766 (which may be part of a flow dividerassembly 774) for a fuel system 50 (or other fuel system) in,respectively, a first configuration (FIG. 20A), a second configuration(FIG. 20B), and a third configuration (FIG. 20C).

FIGS. 21A-21C are schematic cross-sectional views of another embodimentof a flow divider valve 866 (which may be part of a flow dividerassembly 874) for a fuel system 50 (or other fuel system) in,respectively, a first configuration (FIG. 21A), a second configuration(FIG. 21B), and a third configuration (FIG. 21C).

FIGS. 22A-22C are schematic cross-sectional views of another embodimentof a flow divider valve 966 (which may be part of a flow dividerassembly 974) for a fuel system 50 (or other fuel system) in,respectively, a first configuration (FIG. 22A), a second configuration(FIG. 22B), and a third configuration (FIG. 22C).

FIGS. 23A-23C are schematic cross-sectional views of another embodimentof a flow divider valve 1066 (which may be part of a flow dividerassembly 1074) for a fuel system 50 (or other fuel system) in,respectively, a first configuration (FIG. 23A), a second configuration(FIG. 23B), and a third configuration (FIG. 23C).

FIGS. 24A-24C are schematic cross-sectional views of another embodimentof a flow divider valve 1166 (which may be part of a flow dividerassembly 1174) for a fuel system 50 (or other fuel system) in,respectively, a first configuration (FIG. 24A), a second configuration(FIG. 24B), and a third configuration (FIG. 24C).

FIGS. 25A-25C are schematic cross-sectional views of another embodimentof a flow divider valve 1266 (which may be part of a flow dividerassembly 1274) for a fuel system 50 (or other fuel system) in,respectively, a first configuration (FIG. 25A), a second configuration(FIG. 25B), and a third configuration (FIG. 25C).

In reference to FIGS. 17A-25C, springs or spring connections (e.g. coilsprings) are illustrated as dotted lines or circles, wherein closerspaced (packed) circles represented higher stiffness (and/or compressed)springs and wider spaced (packed) circles represent lower stiffness(and/or expanded) springs. The flow divider valves and assemblies aregenerally shown in cross-section in a plane parallel to a longitudinalaxis (indicated by dashed-dot line and labelled L) of the flow dividervalve. In some embodiments, the flow divider valves may be cylindricalwith an extension parallel to the longitudinal axis.

Some operating principles and elements of the flow divider valves ofFIGS. 17A-25C may be similar. Like elements are identified usingreference numerals that are incremented by 100 between sequentialfigures, whenever possible. In the description, reference to multiplereference numerals is meant to be indicative of the respectiveembodiments, where and if applicable. Several or all of the flow dividervalves may share a common aspect (such as analogous feature(s) orelement(s)). In such cases, for conciseness, the common aspect inmultiple embodiments may be referred to at once by multiple referencenumerals. The multiple reference numerals may be referred to usingeither singular or plural forms. For brevity, FIGS. 17A-25A may be usedto refer to FIGS. 17A, 18A, 19A, 20A, 21A, 22A, 23A, 24A, 25A.Similarly, FIGS. 17B-25B and FIGS. 17C-25C may be used to refer tofigures having the same letter.

Fuel may be supplied to the combustor 16 by separate fuel manifolds62A-62B by means of a flow divider valve assembly 474, 574, 674, 774,874, 974, 1074, 1174, 1274 comprising a fuel flow scheduling valve(s)(e.g., flow divider valves 466, 566, 666, 766, 866, 966, 1066, 1166,1266). In some embodiments, the fuel flow scheduling valves incorporatefeatures to control fuel flow to each one of the fuel manifolds 62A-62B,to control the flow and/or pressure of pressurized gas (e.g. from a gasdriven fuel purge system) flowing to each one of the fuel manifolds62A-62B and to control, if necessary, pressure(s) within internalchambers of the flow divider valves 466, 566, 666, 766, 866, 966, 1066,1166, 1266 or fuel flow scheduling valves that contain reference/controlsprings or other components.

Each of the flow divider assemblies 474, 574, 674, 774, 874, 974, 1074,1174, 1274 may be configurable (e.g., actuatable) between a firstconfiguration and a second configuration. Each of the flow dividerassemblies 474, 574, 674, 774, 874, 974, 1074, 1174, 1274 may beconfigurable (e.g., actuatable) to adopt other configurations. The firstand second configurations of the flow divider assemblies 474, 574, 674,774, 874, 974, 1074, 1174, 1274 may correspond to first and secondconfigurations of the respective flow divider valves 466, 566, 666, 766,866, 966, 1066, 1166, 1266. The flow divider valves 466, 566, 666, 766,866, 966, 1066, 1166, 1266 are provided with respective fuel inlets490A, 590, 690, 790, 890, 990, 1090, 1190, 1290; respective pressurizedgas inlets 492A, 592, 692, 792, 892, 992, 1092, 1192, 1292A (e.g. forsupplying pressurized gas for purging fuel manifolds of fuel when therespective fuel inlets are shut-off); respective first outlets 494A,594A, 694A, 794A, 894A, 994A, 1094A, 1194A, 1294A configured to providefluid communication between the respective first chambers 498A, 598A,698A, 798A, 898A, 998A, 1098A, 1198A and, 1298A and the first fuelmanifold 62A; respective second outlets 494B, 594B, 694B, 794B, 894B,994B, 1094B, 1194B, 1294B configured to provide fluid communicationbetween respective second chambers 498B, 598B, 698B, 798B, 898B, 998B,1098B, 1198B, 1298B and the second fuel manifold 62B; respective purgevalves 495A, 495B, 595A, 595B, 695A, 695B, 795A, 795B, 895A, 895B, 995A,995B, 1095A, 1095B, 1195A, 1195B, 1295A, 1295B for discharging purginggas into one or more of the fuel manifolds 62A-62B; and respectivevalves (or valve members) 496B, 596B, 696B, 796B, 896B, 996B, 1096B,1196B, 1296B for at least partially sealing and/or closing therespective first chambers 498A, 598A, 698A, 798A, 898A, 998A, 1098A,1198A, 1298A from the respective second chambers 498B, 598B, 698B, 798B,898B, 998B, 1098B, 1198B, 1298B in the second configuration. In someembodiments, the flow divider valve 466, 566, 666, 766, 866, 966, 1066,1166, 1266 may be a spool-type valve.

In the first configuration (FIGS. 17A-25A), the fuel pressure or flowrate at the fuel inlet 490A, 590, 690, 790, 890, 990, 1090, 1190, 1290is above a second cracking pressure or flow rate. In the secondconfiguration (FIGS. 17B-25B), the fuel pressure or flow rate at thefuel inlet 490A, 590, 690, 790, 890, 990, 1090, 1190, 1290 is between afirst cracking pressure or flow rate and a second cracking pressure orflow rate. In the third configuration (FIGS. 17C-25C), the fuel pressureor flow rate at the fuel inlet 490A, 590, 690, 790, 890, 990, 1090,1190, 1290 is less than the second cracking pressure or flow rate.

In reference to the flow divider valves of FIGS. 17A-25C, seals may beprovided to prevent leakage across valves, spools or other flow controlcomponents. Seals may include gaskets, deformable/resilient sealingmembers, pressure seals, o-rings, or suitable plugs. The seals mayprevent leakage across sealed chambers under expected operatingpressures of the flow divider valves.

The flow divider assembly 474, 574, 674, 774, 874, 974, 1074, 1174, 1274may include a common housing. The one or more purge valve(s) 495B, 595B,695B, 795B, 895B, 995B, 1095B, 1195B, 1295B (or purge valve members) maybe configurable to (e.g. in the second configuration) permit pressurizedgas to flow to the second fuel manifold 62B to flush fuel in the secondfuel manifold 62B into the combustor 16. In various embodiments, thepurge valve 495B, 595B, 695B, 795B, 895B, 995B, 1095B, 1195B, 1295B maybe separate or integrated with the flow divider valve 466, 566, 666,766, 866, 966, 1066, 1166, 1266. The flow divider assembly 474, 574,674, 774, 874, 974, 1074, 1174, 1274 may be configured to, in the firstconfiguration, supply fuel to the first fuel manifold 62A and the secondfuel manifold 62B and to, in the second configuration, stop supplyingfuel to the second fuel manifold 62B while supplying fuel to the firstfuel manifold 62A.

Valve (or valve member) 496B, 596B, 696B, 796B, 896B, 996B, 1096B,1196B, 1296B may be responsive to fuel pressure at the fuel inlet 490A,590, 690, 790, 890, 990, 1090, 1190, 1290, or a differential pressurebetween fuel and pressurized gas pressures to, in the secondconfiguration, stop fuel flow between the first chamber 498A, 598A,698A, 798A, 898A, 998A, 1098A, 1198A, 1298A and the second chamber 498B,598B, 698B, 798B, 898B, 998B, 1098B, 1198B, 1298B. A plurality of spoolsmay together form the valves. The spools may be inter-connected viasuitable connections (e.g., springs). Seals, generally seen in profileas circles on valve member faces or as squares between valve members andwalls in FIGS. 17A-25C, may be provided in the flow divider valve 466,566, 666, 766, 866, 966, 1066, 1166, 1266 to prevent leakage.

The purge valve 495A, 595A, 695A, 795A, 895A, 995A, 1095A, 1195A, 1295Amay be responsive to pressure in the second chamber 498B, 598B, 698B,798B, 898B, 998B, 1098B, 1198B, 1298B to, e.g., in the secondconfiguration, open a purging flow path from the pressurized gas inlet492A, 592, 692, 792, 892, 992, 1092, 1192, 1292A to the second fuelmanifold 62B via the second chamber 498B, 598B, 698B, 798B, 898B, 998B,1098B, 1198B, 1298B.

In reference to FIGS. 17A-25A, the flow divider assembly 474, 574, 674,774, 874, 974, 1074, 1174, 1274 is in a first configuration where thefirst fuel manifold 62A and the second fuel manifold 62B both receivefuel via the flow divider valves. A first fuel path, partially indicatedwith curved arrows with star markers, between the fuel inlet 490A, 590,690, 790, 890, 990, 1090, 1190, 1290 and the first outlet 494A, 594A,694A, 794A, 894A, 994A, 1094A, 1194A, 1294A is open to allow fuel toflow into the first fuel manifold 62A. Additionally, a second fuel path,indicated with curved arrows with star markers followed by the curvedarrow with triangle markers, between the fuel inlet 490A, 590, 690, 790,890, 990, 1090, 1190, 1290 and the second outlet 494B, 594B, 694B, 794B,894B, 994B, 1094B, 1194B, 1294B is open to allow fuel to flow also intothe second fuel manifold 62B.

In the first configuration, fuel pressure at the fuel inlet 490A, 590,690, 790, 890, 990, 1090, 1190, 1290 may be above the second (and first)cracking pressure or flow rate such that the flow divider valve 466,566, 666, 766, 866, 966, 1066, 1166, 1266 may facilitate actuation ofspools (or valves) to open the first and second fuel paths while closingthe purge valve 495B, 595B, 695B, 795B, 895B, 995B, 1095B, 1195B, 1295B.The actuation may be a self-actuation via springs (shown as dottedlines) or other pressure-sensitive or flow-sensitive actuation.

In reference to FIGS. 17B-25B, the flow divider assembly 474, 574, 674,774, 874, 974, 1074, 1174, 1274 is in a second configuration where thefirst fuel manifold 62A may continue to receive fuel while fuel flow tothe second fuel manifold 62B may be stopped and replaced with a flow ofpurging gas. In the second configuration, the first chamber 498A, 598A,698A, 798A, 898A, 998A, 1098A, 1198A, 1298A may be sealed from thesecond chamber 498B, 598B, 698B, 798B, 898B, 998B, 1098B, 1198B, 1298B.The first fuel path, indicated with curved arrows with star markers,between the fuel inlet 490A, 590, 690, 790, 890, 990, 1090, 1190, 1290and the first outlet 494A, 594A, 694A, 794A, 894A, 994A, 1094A, 1194A,1294A may be open with fuel flowing into the first outlet 494A, 594A,694A, 794A, 894A, 994A, 1094A, 1194A, 1294A. The second fuel pathbetween the fuel inlet 490A, 590, 690, 790, 890, 990, 1090, 1190, 1290and the second outlet 494B, 594B, 694B, 794B, 894B, 994B, 1094B, 1194B,1294B may be closed with substantially no fuel flowing from the fuelinlet 490A, 590, 690, 790, 890, 990, 1090, 1190, 1290 into the secondoutlet 494B, 594B, 694B, 794B, 894B, 994B, 1094B, 1194B, 1294B. Apurging flow path, partially indicated with curved arrows with diamondmarkers, may be opened between the pressurized gas inlet 492A, 592, 692,792, 892, 992, 1092, 1192, 1292A and the second outlet 494B, 594B, 694B,794B, 894B, 994B, 1094B, 1194B, 1294B to cause purging gas to flow tothe second fuel manifold 62B and purge/flush fuel therein into thecombustor 16.

In the second configuration, the fuel pressure or flow rate at the fuelinlet 490A, 590, 690, 790, 890, 990, 1090, 1190, 1290 may be below thesecond cracking pressure or flow rate but above the first crackingpressure or flow rate such that the flow divider valve 466, 566, 666,766, 866, 966, 1066, 1166, 1266 may facilitate actuation of spools(valves) to open the first fuel path to the first outlet 494A, 594A,694A, 794A, 894A, 994A, 1094A, 1194A, 1294A while closing the secondfuel path to the second outlet 494B, 594B, 694B, 794B, 894B, 994B,1094B, 1194B, 1294B. The second fuel path may be closed or sealed (atleast partially) via movement of the valve 496B, 596B, 696B, 796B, 896B,996B, 1096B, 1196B, 1296B towards the first chamber 498A, 598A, 698A,798A, 898A, 998A, 1098A, 1198A, 1298A (towards the left) to (sealingly)engage with an opposing wall of the flow divider valve 466, 566, 666,766, 866, 966, 1066, 1166, 1266, and in some embodiments via themovement of the valve 495A, 595A, 695A, 795A, 895A, 995A, 1095A, 1195A,1295A towards the valve 496B, 596B, 696B, 796B, 896B, 996B, 1096B,1196B, 1296B or reciprocally or mutually, which closes/stops fluidcommunication between first and second chambers 498A, 498B, 598A, 598B,698A, 698B, 798A, 798B, 898A, 898B, 998A, 998B, 1098A, 1098B, 1198A,1198B, 1298A, 1298B.

The purging flow path may be opened via movement of the purge valve495B, 595B, 695B, 795B, 895B, 995B, 1095B, 1195B, 1295B to open thepressurized gas inlet 492A, 592, 692, 792, 892, 992, 1092, 1192, 1292A.The movement may be actuated (via spring force) due to a lower pressurein the second chamber 498B, 598B, 698B, 798B, 898B, 998B, 1098B, 1198B,1298B after sealing from the first chamber 498A, 598A, 698A, 798A, 898A,998A, 1098A, 1198A, 1298A.

In reference to FIGS. 17C-25C, the flow divider assembly 474, 574, 674,774, 874, 974, 1074, 1174, 1274 is in a third configuration where fuelsupply to both the first fuel manifold 62A and the second fuel manifold62B may be stopped and replaced with a supply of purging gas. The thirdconfiguration may be useful during shut down of GTE 10.

In the third configuration, the first chamber 498A, 598A, 698A, 798A,898A, 998A, 1098A, 1198A, 1298A and the second chamber 498B, 598B, 698B,798B, 898B, 998B, 1098B, 1198B, 1298B may be in fluid communication. Thefuel inlet 490A, 590, 690, 790, 890, 990, 1090, 1190, 1290 may be closedby actuation of the (e.g. spool) valve. The purging flow path, indicatedwith curved arrows with diamond markers, is open between the pressurizedgas inlet 492A, 592, 692, 792, 892, 992, 1092, 1192, 1292A and thesecond outlet 494B, 594B, 694B, 794B, 894B, 994B, 1094B, 1194B, 1294B tocause purging gas to flow to the second fuel manifold 62B andpurge/flush fuel therein into the combustor 16. An additional purgingflow path, indicated with curved arrows with circle markers, is openbetween the pressurized gas inlet 492A, 592, 692, 792, 892, 992, 1092,1192, 1292A and the first outlet 494A, 594A, 694A, 794A, 894A, 994A,1094A, 1194A, 1294A to cause purging gas to flow to the first fuelmanifold 62A and purge/flush fuel therein into the combustor 16. In someembodiments, the third configuration of the flow divider valve 466, 566,666, 766, 866, 966, 1066, 1166, 1266 may be used during shutdown of theGTE 10.

In the third configuration, fuel pressure or flow rate at the fuel inlet490A, 590, 690, 790, 890, 990, 1090, 1190, 1290 may be below the first(and second) cracking pressure or flow rate such that the flow dividervalve 466, 566, 666, 766, 866, 966, 1066, 1166, 1266 facilitatesactuation of the (e.g. spool) valves to close the first and second fuelpaths while opening pressurized gas inlet 492A, 592, 692, 792, 892, 992,1092, 1192, 1292A and allowing fluid communication between the first andsecond chambers 498A, 498B, 598A, 598B, 698A, 698B, 798A, 798B, 898A,898B, 998A, 998B, 1098A, 1098B, 1198A, 1198B, 1298A, 1298B. Theactuation may be a self-actuation, e.g. via springs adapted to respondto the cracking pressure or flow rate by deforming to generate suitablevalve displacement(s) that open, closes or modifies flow paths based onthe fuel pressure or flow rate.

In reference to FIGS. 17A-17C, the purge valve 495A, 495B and the valves496A, 496B are selectively actuatable via differential pressure sensingdevices 493A, 493B, respectively comprising pistons 491A, 491B withsensing ports in the form of inlets 492B, 492C, 490B. Respective facesof the pistons 491A, 491B may be exposed to lower pressure viarespective inlets 492C, 490B. Another face of the piston 491B may beexposed to the pressurized gas.

Similarly, in reference to FIGS. 25A-25C, the valves 1295A, 1296A may beselectively actuatable via differential pressure sensing device 1293,comprising a piston 1291 exposed to a sensing port in the form of inlet1292B, which may be exposed to a lower pressure source such as anaircraft fuel tank, or a Fuel Control Unit (FCU) inlet or a location ata lower pressure than the respective fuel inlet 492B, 492C, 490B, 1290.

In reference to FIGS. 17A-17C, 22A-22C, 23A-23C and 24A-24C, respectivepurge holes 497, 997, 1097, 1197A, 1197B selectively openable via therespective purge valves 495A, 995A, 1095A, 1195A may facilitate flowcommunication between the first and second chambers 498A and 498B, 998Aand 998B, 1098A and 1098B, and 1198A and 1198B respectively. The purgevalve 1095A may comprise adjacent, cooperating walls configurable toblock the purge hole 1097.

In reference to FIGS. 23A-23C and 24A-24C, springs may be at leastpartially enclosed in respective spring chambers 1089, 1189A, 1189B thatmay be exposed to lower pressure relative to the fuel pressure. Thespring chambers 1189A, 1189B may be fluidly separated/sealed.

In reference to FIGS. 17A-25C, various embodiments and/or aspects offlow divider valves 466, 566, 666, 766, 866, 966, 1066, 1166, 1266described herein may be used or be implemented in relation to one ormore of methods 2000, 3000, 4000, 5000, 6000, 6050, 7000, 8000, and/or9000 described herein.

For instance, in reference to FIGS. 11 and 17A-25C, some aspects and/orembodiments of the method 6000 may include using only one flow dividervalve 466, 566, 666, 766, 866, 966, 1066, 1166, 1266 for: supplying fuelto the combustor 16 by supplying fuel to the first and second fuelmanifolds 62A, 62B; and while supplying fuel to the combustor 16 bysupplying fuel to the first fuel manifold 62A: stopping supplying fuelto the second fuel manifold 62B, and supplying pressurized gas to thesecond fuel manifold 62B to flush fuel in the second fuel manifold 62Binto the combustor 16.

For example, in some embodiments of the method 6000, the flow dividervalve 466, 566, 666, 766, 866, 966, 1066, 1166, 1266 may be a spool-typevalve including a plurality of spools. In some embodiments, the flowdivider valve 466, 566, 666, 766, 866, 966, 1066, 1166, 1266 maycomprise at least two spools where each of the two spools are configuredto be responsive to fuel pressure at one or more fuel inlet(s) 490A,590, 690, 790, 890, 990, 1090, 1190, 1290 of the flow divider valve 466,566, 666, 766, 866, 966, 1066, 1166, 1266 and pressure at one or morepressurized gas inlet(s) 492A, 592, 692, 792, 892, 992, 1092, 1192,1292A. Some embodiments of the method 6000 may include, while supplyingfuel to the flow divider valve 466, 566, 666, 766, 866, 966, 1066, 1166,1266 via the fuel inlet 490A, 590, 690, 790, 890, 990, 1090, 1190, 1290:using a first outlet 494A, 594A, 694A, 794A, 894A, 994A, 1094A, 1194A,1294A of the flow divider valve 466, 566, 666, 766, 866, 966, 1066,1166, 1266 to supply fuel to the first fuel manifold 62A; and using asecond outlet 494B, 594B, 694B, 794B, 894B, 994B, 1094B, 1194B, 1294B ofthe flow divider valve 466, 566, 666, 766, 866, 966, 1066, 1166, 1266 tosupply fuel to the second fuel manifold 62B.

Some embodiments of the method 6000 may include, while keeping a firstfuel flow path between the fuel inlet 490A, 590, 690, 790, 890, 990,1090, 1190, 1290 and the first outlet 494A, 594A, 694A, 794A, 894A,994A, 1094A, 1194A, 1294A of the flow divider valve 466, 566, 666, 766,866, 966, 1066, 1166, 1266 open to continue to supply fuel to the firstfuel manifold 62A: reducing fuel pressure at the fuel inlet 490A, 590,690, 790, 890, 990, 1090, 1190, 1290 to cause the flow divider valve466, 566, 666, 766, 866, 966, 1066, 1166, 1266 to close a second fuelflow path between the fuel inlet 490A, 590, 690, 790, 890, 990, 1090,1190, 1290 and the second outlet 494B, 594B, 694B, 794B, 894B, 994B,1094B, 1194B, 1294B, and opening a gas flow path via the second outlet494B, 594B, 694B, 794B, 894B, 994B, 1094B, 1194B, 1294B of the flowdivider valve 466, 566, 666, 766, 866, 966, 1066, 1166, 1266 between thesecond fuel manifold 62B and the pressurized gas inlet 492A, 592, 692,792, 892, 992, 1092, 1192, 1292A of the flow divider valve 466, 566,666, 766, 866, 966, 1066, 1166, 1266.

Some embodiments of the method 6000 may include, while supplying fuel tothe flow divider valve 466, 566, 666, 766, 866, 966, 1066, 1166, 1266via the fuel inlet 490A, 590, 690, 790, 890, 990, 1090, 1190, 1290 ofthe flow divider valve 466, 566, 666, 766, 866, 966, 1066, 1166, 1266,reducing fuel pressure at the fuel inlet 490A, 590, 690, 790, 890, 990,1090, 1190, 1290 to between a first prescribed cracking pressure and asecond prescribed cracking pressure to cause the flow divider valve 466,566, 666, 766, 866, 966, 1066, 1166, 1266 to close the second fuel flowpath between the fuel inlet 490A, 590, 690, 790, 890, 990, 1090, 1190,1290 and the second outlet 494B, 594B, 694B, 794B, 894B, 994B, 1094B,1194B, 1294B. Some embodiments of the method 6000 may include, whilefuel pressure at the fuel inlet 490A, 590, 690, 790, 890, 990, 1090,1190, 1290 is between the first cracking pressure and the secondcracking pressure, reducing pressure in the (second) chamber 498B, 598B,698B, 798B, 898B, 998B, 1098B, 1198B, 1298B of the flow divider valve466, 566, 666, 766, 866, 966, 1066, 1166, 1266 to actuate a purge valve495B, 595B, 695B, 795B, 895B, 995B, 1095B, 1195B, 1295B to open thepressurized gas inlet 492A, 592, 692, 792, 892, 992, 1092, 1192, 1292Ato the (second) chamber 498B, 598B, 698B, 798B, 898B, 998B, 1098B,1198B, 1298B and open the gas flow path between the second fuel manifold62B and the pressurized gas inlet 492A, 592, 692, 792, 892, 992, 1092,1192, 1292A.

The embodiments described in this document provide non-limiting examplesof possible implementations of the present technology. Upon review ofthe present disclosure, a person of ordinary skill in the art willrecognize that changes may be made to the embodiments described hereinwithout departing from the scope of the present technology. For example,embodiments multi-engine power plants may include more than two engineswherein the engines may be configured to directly or indirectly drive acommon load, purge valves may be solenoid valves, hydraulically actuatedvalves, or another types of flow control device used for controllingflows (including substantially stopping flows), the embodiments of flowdivider valves may use non-spring means for interconnection. Yet furthermodifications could be implemented by a person of ordinary skill in theart in view of the present disclosure, which modifications would bewithin the scope of the present technology.

What is claimed is:
 1. A method of operating a gas turbine engine, thegas turbine engine having a first fuel manifold and a second fuelmanifold configured to supply fuel to a combustor of the gas turbineengine, the method comprising: supplying air from a compressor sectionof the gas turbine engine to the combustor; supplying fuel to thecombustor by supplying fuel to the first and second fuel manifolds;while supplying fuel to the combustor by supplying fuel to the firstfuel manifold: stopping supplying fuel to the second fuel manifold; andusing a pump other than the compressor section of the gas turbine engineto drive gas into the second fuel manifold to flush fuel in the secondfuel manifold into the combustor.
 2. The method of claim 1, comprisingusing a flow divider valve to stop supplying fuel to the second fuelmanifold and to supply fuel to the first fuel manifold.
 3. The method ofclaim 1, wherein the gas turbine engine is mounted to an aircraft andthe method is executed during flight of the aircraft.
 4. The method ofclaim 3, wherein: the aircraft is a rotary wing aircraft; the gasturbine engine is a first gas turbine engine; a second gas turbineengine is mounted to the aircraft; and the method includes: operatingthe first gas turbine engine in a low-power mode of operation while fuelis supplied to the first fuel manifold and fuel supply to the secondfuel manifold is stopped; and operating the second gas turbine engine ina high-power mode of operation while the first gas turbine engine isoperated in the low-power mode of operation.
 5. The method of claim 1,comprising, after fuel in the second fuel manifold is flushed into thecombustor and while continuing to supply fuel to the combustor bysupplying fuel to the first fuel manifold, stopping the using of thepump to drive gas into the second fuel manifold.
 6. The method of claim1, comprising supplying the gas from the pump to a fuel line at alocation between a flow divider valve and the second fuel manifold. 7.The method of claim 1, comprising, after fuel in the second fuelmanifold is flushed into the combustor and while supplying fuel to thesecond fuel manifold is stopped, continuing to supply fuel to thecombustor by supplying fuel to the first fuel manifold.
 8. The method ofclaim 1, wherein at least a majority of the gas is air.
 9. A method ofoperating a multi-engine system of an aircraft, the multi-engine systemincluding a first gas turbine engine (FGTE) and a second gas turbineengine (SGTE) drivingly connected to a common load, the methodcomprising: operating the FGTE and the SGTE to drive the common load,operating the SGTE including supplying fuel to a combustor of the SGTEby supplying fuel to a first fuel manifold and a second fuel manifold ofthe SGTE; while operating the FGTE and supplying fuel to the combustorof the SGTE by supplying fuel to the first fuel manifold of the SGTE:stopping supplying fuel to the second fuel manifold of the SGTE; andusing a pump to drive gas into the second fuel manifold of the SGTE toflush fuel in the second fuel manifold into the combustor of the SGTE.10. The method of claim 9, comprising using a flow divider valve to stopsupplying fuel to the second fuel manifold and to supply fuel to thefirst fuel manifold.
 11. The method of claim 9, wherein the common loadincludes a rotary wing of the aircraft and the method is executed duringflight of the aircraft.
 12. The method of claim 9, comprising, afterfuel in the second fuel manifold is flushed and while continuing tosupply fuel to the combustor of the SGTE by supplying fuel to the firstfuel manifold, stopping the using of the pump to drive gas into thesecond fuel manifold.
 13. The method of claim 9, comprising supplyingthe gas from the pump to a fuel line at a location between a flowdivider valve and the second fuel manifold.
 14. The method of claim 9,comprising, after fuel in the second fuel manifold is flushed and whilesupplying fuel to the second fuel manifold is stopped, continuing tosupply fuel to the combustor of the SGTE by supplying fuel to the firstfuel manifold.
 15. A gas turbine engine comprising: a compressor sectionfor pressurizing air; a combustor in which the pressurized air is mixedwith fuel and ignited for generating an annular stream of combustiongases; a turbine for extracting energy from the combustion gases; afirst fuel manifold configured to supply fuel to the combustor; a secondfuel manifold configured to supply fuel to the combustor; one or morevalves actuatable between a first configuration and a secondconfiguration, the one or more valves configured to supply fuel to thefirst and second fuel manifolds in the first configuration, the one ormore valves configured to supply fuel to the first fuel manifold andstop supplying fuel to the second fuel manifold in the secondconfiguration; and a pump other than the compressor section andconfigured to, in the second configuration of the one or more valves,drive gas into the second fuel manifold to flush fuel in the second fuelmanifold into the combustor.
 16. The gas turbine engine of claim 15,comprising a fuel line establishing fluid communication between a firstof the one or more valves and the second fuel manifold, the pumpconfigured to discharge the gas into the fuel line at a locationdownstream of the first valve.
 17. The gas turbine engine of claim 15,wherein the pump is electrically driven by an electric motor.